Consolidate documentation (#3071)

* 🔥 consolidate documentation
* ♻️ overwork std specializations
* 🚚 move images files to mkdocs
* ♻️ fix URLs
* 🔧 tweak MkDocs configuration
* 🔧 add namespaces
* 📝 document deprecations
* 📝 document documentation generation
* 🚸 improve search
* 🚸 add examples
* 🚧 start adding documentation for macros
* 📝 add note for https://github.com/nlohmann/json/issues/874#issuecomment-1001699139
* 📝 overwork example handling
* 📝 fix Markdown tables

doc/mkdocs/docs/api/json_pointer/to_string.md

@@ -0,0 +1,39 @@
+# <small>nlohmann::json_pointer::</small>to_string
+
+```cpp
+std::string to_string() const;
+```
+
+Return a string representation of the JSON pointer.
+
+## Return value
+
+A string representation of the JSON pointer
+
+## Notes
+
+For each JSON pointer `ptr`, it holds:
+
+```cpp
+ptr == json_pointer(ptr.to_string());
+```
+
+## Examples
+
+??? example
+
+    The example shows the result of `to_string`.
+     
+    ```cpp
+    --8<-- "examples/json_pointer__to_string.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/json_pointer__to_string.output"
+    ```
+
+## Version history
+
+Since version 2.0.0.