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

[Baranov Victor via cfe-commits]

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

lets add sentence that const can be redundant when variable is already constexpr.

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