Reorganize directories (#3462)

* 🚚 move files
* 🚚 rename doc folder to docs
* 🚚 rename test folder to tests

README.md

@@ -1,4 +1,4 @@
-[![JSON for Modern C++](https://raw.githubusercontent.com/nlohmann/json/master/doc/json.gif)](https://github.com/nlohmann/json/releases)
+[![JSON for Modern C++](docs/json.gif)](https://github.com/nlohmann/json/releases)
 
 [![Build Status](https://ci.appveyor.com/api/projects/status/1acb366xfyg3qybk/branch/develop?svg=true)](https://ci.appveyor.com/project/nlohmann/json)
 [![Ubuntu](https://github.com/nlohmann/json/workflows/Ubuntu/badge.svg)](https://github.com/nlohmann/json/actions?query=workflow%3AUbuntu)
@@ -54,7 +54,7 @@ There are myriads of [JSON](https://json.org) libraries out there, and each may
 
 - **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.
 
-- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/test/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
+- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
 
 Other aspects were not so important to us:
 
@@ -83,7 +83,7 @@ Thanks everyone!
 
 :question: If you have a **question**, please check if it is already answered in the [**FAQ**](https://json.nlohmann.me/home/faq/) or the [**Q&A**](https://github.com/nlohmann/json/discussions/categories/q-a) section. If not, please [**ask a new question**](https://github.com/nlohmann/json/discussions/new) there.
 
-:books: If you want to **learn more** about how to use the library, check out the rest of the [**README**](#examples), have a look at [**code examples**](https://github.com/nlohmann/json/tree/develop/doc/examples), or browse through the [**help pages**](https://json.nlohmann.me).
+:books: If you want to **learn more** about how to use the library, check out the rest of the [**README**](#examples), have a look at [**code examples**](https://github.com/nlohmann/json/tree/develop/docs/examples), or browse through the [**help pages**](https://json.nlohmann.me).
 
 :construction: If you want to understand the **API** better, check out the [**API Reference**](https://json.nlohmann.me/api/basic_json/).
 
@@ -93,7 +93,7 @@ There is also a [**docset**](https://github.com/Kapeli/Dash-User-Contributions/t
 
 ## Examples
 
-Beside the examples below, you may want to check the [documentation](https://json.nlohmann.me/) where each function contains a separate code example (e.g., check out [`emplace()`](https://json.nlohmann.me/api/basic_json/emplace/)). All [example files](https://github.com/nlohmann/json/tree/develop/doc/examples) can be compiled and executed on their own (e.g., file [emplace.cpp](https://github.com/nlohmann/json/blob/develop/doc/examples/emplace.cpp)).
+Beside the examples below, you may want to check the [documentation](https://json.nlohmann.me/) where each function contains a separate code example (e.g., check out [`emplace()`](https://json.nlohmann.me/api/basic_json/emplace/)). All [example files](https://github.com/nlohmann/json/tree/develop/docs/examples) can be compiled and executed on their own (e.g., file [emplace.cpp](https://github.com/nlohmann/json/blob/develop/docs/examples/emplace.cpp)).
 
 ### JSON as first-class data type
 
@@ -857,7 +857,7 @@ namespace nlohmann {
 
 #### Can I write my own serializer? (Advanced use)
 
-Yes. You might want to take a look at [`unit-udt.cpp`](https://github.com/nlohmann/json/blob/develop/test/src/unit-udt.cpp) in the test suite, to see a few examples.
+Yes. You might want to take a look at [`unit-udt.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-udt.cpp) in the test suite, to see a few examples.
 
 If you write your own serializer, you'll need to do a few things:
 
@@ -1329,7 +1329,7 @@ Only if your request would contain confidential information, please [send me an
 
 I deeply appreciate the help of the following people.
 
-<img src="https://raw.githubusercontent.com/nlohmann/json/develop/doc/avatars.png" align="right">
+<img src="https://raw.githubusercontent.com/nlohmann/json/develop/docs/avatars.png" align="right">
 
 - [Teemperor](https://github.com/Teemperor) implemented CMake support and lcov integration, realized escape and Unicode handling in the string parser, and fixed the JSON serialization.
 - [elliotgoodrich](https://github.com/elliotgoodrich) fixed an issue with double deletion in the iterator classes.