Reorganize directories (#3462)

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* 🚚 rename test folder to tests

docs/mkdocs/docs/api/basic_json/dump.md

@@ -0,0 +1,79 @@
+# <small>nlohmann::basic_json::</small>dump
+
+```cpp
+string_t dump(const int indent = -1,
+              const char indent_char = ' ',
+              const bool ensure_ascii = false,
+              const error_handler_t error_handler = error_handler_t::strict) const;
+```
+
+Serialization function for JSON values. The function tries to mimic Python's
+[`json.dumps()` function](https://docs.python.org/2/library/json.html#json.dump), and currently  supports its `indent`
+and `ensure_ascii` parameters.
+    
+## Parameters
+
+`indent` (in)
+:   If `indent` is nonnegative, then array elements and object members will be pretty-printed with that indent level. An
+    indent level of `0` will only insert newlines. `-1` (the default) selects the most compact representation.
+
+`indent_char` (in)
+:   The character to use for indentation if `indent` is greater than `0`. The default is ` ` (space).
+
+`ensure_ascii` (in)
+:   If `ensure_ascii` is true, all non-ASCII characters in the output are escaped with `\uXXXX` sequences, and the
+    result consists of ASCII characters only.
+
+`error_handler` (in)
+:   how to react on decoding errors; there are three possible values (see [`error_handler_t`](error_handler_t.md):
+    `strict` (throws and exception in case a decoding error occurs; default), `replace` (replace invalid UTF-8 sequences
+    with U+FFFD), and `ignore` (ignore invalid UTF-8 sequences during serialization; all bytes are copied to the output
+    unchanged)).
+    
+## Return value
+
+string containing the serialization of the JSON value
+
+## Exception safety
+
+Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
+
+## Exceptions
+
+Throws [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) if a string stored inside the JSON value
+is not UTF-8 encoded and `error_handler` is set to `strict`
+
+## Complexity
+
+Linear.
+
+## Notes
+
+Binary values are serialized as object containing two keys:
+
+- "bytes": an array of bytes as integers
+- "subtype": the subtype as integer or `#!json null` if the binary has no subtype
+
+## Examples
+
+??? example
+
+    The following example shows the effect of different `indent`, `indent_char`, and `ensure_ascii` parameters to the
+    result of the serialization.
+
+    ```cpp
+    --8<-- "examples/dump.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/dump.output"
+    ```
+
+## Version history
+
+- Added in version 1.0.0.
+- Indentation character `indent_char`, option `ensure_ascii` and exceptions added in version 3.0.0.
+- Error handlers added in version 3.4.0.
+- Serialization of binary values added in version 3.8.0.