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/basic_json/to_string.md

@@ -0,0 +1,65 @@
+# to_string(basic_json)
+
+```cpp
+template <typename BasicJsonType>
+std::string to_string(const BasicJsonType& j);
+```
+
+This function implements a user-defined to_string for JSON objects.
+
+## Template parameters
+
+`BasicJsonType`
+:   a specialization of [`basic_json`](index.md)
+
+## 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
+
+## Complexity
+
+Linear.
+
+## Possible implementation
+
+```cpp
+template <typename BasicJsonType>
+std::string to_string(const BasicJsonType& j)
+{
+    return j.dump();
+}
+```
+
+## Examples
+
+??? example
+
+    The following code shows how the library's `to_string()` function integrates with others, allowing
+    argument-dependent lookup.
+     
+    ```cpp
+    --8<-- "examples/to_string.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/to_string.output"
+    ```
+
+## See also
+
+- [dump](dump.md)
+
+## Version history
+
+Added in version 3.7.0.