[clang-tools-extra] [clang-tidy] Add llvm-regex check (PR #207407)

[via cfe-commits]

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@@ -247,6 +247,12 @@ New checks
   derived type thereof. Also does similar analysis for calls to ``isa<>`` that
   always return ``true``.
 
+- New :doc:`llvm-invalid-regex-pattern
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furtib wrote:

I have rebased from main, migrating all documentation to the markdown format.

https://github.com/llvm/llvm-project/pull/207407