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/operator_string.md

@@ -0,0 +1,24 @@
+# <small>nlohmann::json_pointer::</small>operator std::string
+
+```cpp
+operator std::string() const
+```
+
+Return a string representation of the JSON pointer.
+
+## Return value
+
+A string representation of the JSON pointer
+
+## Possible implementation
+
+```cpp
+operator std::string() const
+{
+    return to_string();
+}
+```
+
+## Version history
+
+Since version 2.0.0.