Reorganize directories (#3462)

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

docs/mkdocs/docs/api/basic_json/parse_error.md

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+# <small>nlohmann::basic_json::</small>parse_error
+
+```cpp
+class parse_error : public exception;
+```
+
+This exception is thrown by the library when a parse error occurs. Parse errors can occur during the deserialization of
+JSON text, BSON, CBOR, MessagePack, UBJSON, as well as when using JSON Patch.
+
+Member `byte` holds the byte index of the last read character in the input file (see note below).
+
+Exceptions have ids 1xx (see [list of parse errors](../../home/exceptions.md#parse-errors)).
+
+```plantuml
+std::exception <|-- basic_json::exception
+basic_json::exception <|-- basic_json::parse_error
+basic_json::exception <|-- basic_json::invalid_iterator
+basic_json::exception <|-- basic_json::type_error
+basic_json::exception <|-- basic_json::out_of_range
+basic_json::exception <|-- basic_json::other_error
+
+interface std::exception {}
+
+class basic_json::exception {
+    + const int id
+    + const char* what() const
+}
+
+class basic_json::parse_error #FFFF00 {
+    + const std::size_t byte
+}
+```
+
+## Member functions
+
+- **what** - returns explanatory string
+
+## Member variables
+
+- **id** - the id of the exception
+- **byte** - byte index of the parse error
+
+## Notes
+
+For an input with $n$ bytes, 1 is the index of the first character and $n+1$ is the index of the terminating null byte
+or the end of file. This also holds true when reading a byte vector for binary formats.
+
+## Examples
+
+??? example
+
+    The following code shows how a `parse_error` exception can be caught.
+    
+    ```cpp
+    --8<-- "examples/parse_error.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/parse_error.output"
+    ```
+
+## See also
+
+- [List of parse errors](../../home/exceptions.md#parse-errors)
+- [`invalid_iterator`](invalid_iterator.md) for exceptions indicating errors with iterators
+- [`type_error`](type_error.md) for exceptions indicating executing a member function with a wrong type
+- [`out_of_range`](out_of_range.md) for exceptions indicating access out of the defined range
+- [`other_error`](other_error.md) for exceptions indicating other library errors
+
+## Version history
+
+- Since version 3.0.0.