Reorganize directories (#3462)

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

docs/examples/flatten.output

@@ -0,0 +1,12 @@
+{
+    "/answer/everything": 42,
+    "/happy": true,
+    "/list/0": 1,
+    "/list/1": 0,
+    "/list/2": 2,
+    "/name": "Niels",
+    "/nothing": null,
+    "/object/currency": "USD",
+    "/object/value": 42.99,
+    "/pi": 3.141
+}