[clang-tools-extra] [llvm] [llvm] add support for mustache templating language (PR #105893)

[via llvm-commits]

cor3ntin wrote:

Did you consider using raw_ostream instead of String? in any case i agree that you should not use SmallString<0> over std::string (std::string will be more efficient as it always has a small buffer - not that you are likely to be able to use it in this use case)

https://github.com/llvm/llvm-project/pull/105893