[clang-tools-extra] [clang-tidy] Adds readability-redundant-const check (PR #189733)

[Baranov Victor via cfe-commits]

================
@@ -0,0 +1,49 @@
+.. title:: clang-tidy - readability-redundant-const
+
+readability-redundant-const
+===========================
+
+Detects redundant ``const`` specifiers on variable declarations.
+
+Examples:
+
+.. code-block:: c++
+
+   // Finds:
----------------
vbvictor wrote:

only `// Finds:` part, I don't remember any other docs do that (and imho it's obvious).
`Replace` and everything else is fine

https://github.com/llvm/llvm-project/pull/189733