Mention run-clang-tidy

Author: vkucera

docs/tools/README.md

@@ -73,6 +73,7 @@ parallel "clang-tidy --fix -checks=-*,misc-include-cleaner {}; echo \"{} \$?\""
 ```
 
 The [`parallel`](https://www.gnu.org/software/parallel/) command is used to parallelise the execution of the `clang-tidy` command for all files.
+Alternatively, you can use the [`run-clang-tidy`](https://clang.llvm.org/extra/clang-tidy/#running-clang-tidy-in-parallel) script to parallelise the `clang-tidy` invocations.
 
 For each file, `clang-tidy` will first try to compile it and then run the enabled check(s) and fix found problems (the `--fix` option).
 The messages are redirected into `clang-tidy.log`.