Reorganize directories (#3462)

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

.github/external_ci/.drone.yml

@@ -0,0 +1,22 @@
+kind: pipeline
+name: test-on-arm64
+
+platform:
+  arch: arm64
+
+steps:
+- name: build
+  image: gcc
+  commands:
+  - wget https://github.com/Kitware/CMake/releases/download/v3.20.2/cmake-3.20.2.tar.gz
+  - tar xfz cmake-3.20.2.tar.gz
+  - cd cmake-3.20.2
+  - ./configure
+  - make cmake ctest -j10
+  - cd ..
+  - mkdir build
+  - cd build
+  - ../cmake-3.20.2/bin/cmake .. -DJSON_FastTests=ON
+  - make -j10
+  - cd tests
+  - ../../cmake-3.20.2/bin/ctest -j10