[clang-tools-extra] readability-identifier-naming should add universal default options (PR #171686)

[Baranov Victor via cfe-commits]

================
@@ -44,6 +44,35 @@ settings. The options and their corresponding values are:
  - ``LowerCase`` - example: ``int i_Variable``
  - ``CamelCase`` - example: ``int IVariable``
 
+The check only works on kinds of identifiers which have been configured,
+so an empty config effectively disables it.
+The "default" option can be used to enable all kinds of identifiers,
+then optionally override specific kinds which are desired with a different case.
+
+For example using values of:
+
+    - DefaultCase of ``lower_case``
+    - MacroDefinitionCase of ``UPPER_CASE``
+    - TemplateParameterCase of ``CamelCase``
+
+Identifies and/or transforms names as follows:
+
+Before:
+
+.. code-block:: c++
+
+    #define macroDefinition
+    template <typename typenameParameter>
+    int functionDeclaration(typenameParameter paramVal, int paramCount);
----------------
vbvictor wrote:

```suggestion
  #define macroDefinition
  template <typename typenameParameter>
  int functionDeclaration(typenameParameter paramVal, int paramCount);
```

https://github.com/llvm/llvm-project/pull/171686