[clang] [llvm] [clang-format] Add CI check confirming ClangFormatStyleOptions.rst is up-to-date. (PR #111513)

[Owen Pan via cfe-commits]

owenca wrote:

> @owenca, see what you think.

IMO it would be more helpful to add the build target to `lib/Format/CMakeLists.txt` instead. For example,
```
$ ninja FormatTests
[1/1] cd /Users/Owen/llvm-project/clang....12/bin/python3.12 dump_format_style.p
$ 
```

https://github.com/llvm/llvm-project/pull/111513