[clang-tools-extra] Add clang-tidy external examples (PR #106675)

[via cfe-commits]

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+=======================
+External Clang-Tidy Examples
+=======================
+
+Introduction
+============
+
+This page provides examples of what people have done with `clang-tidy` that 
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EugeneZelenko wrote:

:program:`clang-tidy`. Same in other places.

https://github.com/llvm/llvm-project/pull/106675