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/exception.md

@@ -1,4 +1,4 @@
-# basic_json::exception
+# <small>nlohmann::basic_json::</small>exception
 
 ```cpp
 class exception : public std::exception;
@@ -44,7 +44,13 @@ Subclasses:
 
 - **id** - the id of the exception
 
-## Example
+## Notes
+
+To have nothrow-copy-constructible exceptions, we internally use `std::runtime_error` which can cope with
+arbitrary-length error messages. Intermediate strings are built with static functions and then passed to the actual
+constructor.
+
+## Examples
 
 ??? example
 
@@ -60,6 +66,10 @@ Subclasses:
     --8<-- "examples/exception.output"
     ```
 
+## See also
+
+[List of exceptions](127.0.0.1:8000/home/exceptions/)
+
 ## Version history
 
 - Since version 3.0.0.