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_slash.md

@@ -0,0 +1,64 @@
+# <small>nlohmann::json_pointer::</small>operator/
+
+```cpp
+// (1)
+json_pointer operator/(const json_pointer& lhs, const json_pointer& rhs);
+
+// (2)
+json_pointer operator/(const json_pointer& lhs, std::string token);
+
+// (3)
+json_pointer operator/(const json_pointer& lhs, std::size_t array_idx);
+```
+
+1. create a new JSON pointer by appending the right JSON pointer at the end of the left JSON pointer
+2. create a new JSON pointer by appending the unescaped token at the end of the JSON pointer
+3. create a new JSON pointer by appending the array-index-token at the end of the JSON pointer
+
+## Parameters
+
+`lhs` (in)
+:    JSON pointer
+
+`rhs` (in)
+:    JSON pointer to append
+
+`token` (in)
+:    reference token to append
+
+`array_idx` (in)
+:    array index to append
+
+## Return value
+
+1. a new JSON pointer with `rhs` appended to `lhs`
+2. a new JSON pointer with unescaped `token` appended to `lhs`
+3. a new JSON pointer with `array_idx` appended to `lhs`
+
+## Complexity
+
+1. Linear in the length of `lhs` and `rhs`.
+2. Linear in the length of `lhs`.
+3. Linear in the length of `lhs`.
+
+## Examples
+
+??? example
+
+    The example shows the usage of `operator/`.
+     
+    ```cpp
+    --8<-- "examples/json_pointer__operator_add_binary.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/json_pointer__operator_add_binary.output"
+    ```
+
+## Version history
+
+1. Added in version 3.6.0.
+2. Added in version 3.6.0.
+3. Added in version 3.6.0.