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/is_primitive.md

@@ -1,4 +1,4 @@
-# basic_json::is_primitive
+# <small>nlohmann::basic_json::</small>is_primitive
 
 ```cpp
 constexpr bool is_primitive() const noexcept;
@@ -38,7 +38,7 @@ The term *primitive* stems from [RFC 8259](https://tools.ietf.org/html/rfc8259):
 This library extends primitive types to binary types, because binary types are  roughly comparable to strings. Hence,
 `is_primitive()` returns `#!cpp true` for binary values.
 
-## Example
+## Examples
 
 ??? example
 
@@ -54,6 +54,15 @@ This library extends primitive types to binary types, because binary types are
     --8<-- "examples/is_primitive.output"
     ```
 
+## See also
+
+- [is_structured()](is_structured.md) returns whether JSON value is structured
+- [is_null()](is_null.md) returns whether JSON value is `null`
+- [is_string()](is_string.md) returns whether JSON value is a string
+- [is_boolean()](is_boolean.md) returns whether JSON value is a boolean
+- [is_number()](is_number.md) returns whether JSON value is a number
+- [is_binary()](is_binary.md) returns whether JSON value is a binary array
+
 ## Version history
 
 - Added in version 1.0.0.