[clang-tools-extra] [clang-tidy] Add modernize-nlohmann-json-explicit-conversions check (PR #126425)

[Mike Crowe via cfe-commits]

mikecrowe wrote:

Thanks for the reviews. I have been able to turn this check into a plugin successfully and I will propose that it is included with the nlohmann/json library.

https://github.com/llvm/llvm-project/pull/126425