Add pre commit hooks to readme (facebook#462)

Summary:
I've recently added support for ktfmt to pre-commit hooks.

macisamuele/language-formatters-pre-commit-hooks#196

I thought it'd be worth mentioning in the README.

Pull Request resolved: facebook#462

Reviewed By: cortinico

Differential Revision: D56680818

Pulled By: hick209

fbshipit-source-id: 3d6482e3d550b5d04647d6582ac3348aac52f9c4

README.md

@@ -79,6 +79,10 @@ Alternatively, you can use [Spotless](https://github.com/diffplug/spotless) with
 
 Consider using [Spotless](https://github.com/diffplug/spotless) with the [ktfmt Maven plugin](https://github.com/diffplug/spotless/tree/main/plugin-maven#ktfmt).
 
+### using pre-commit hooks
+
+A [pre-commit hook](https://pre-commit.com/hooks.html) is implemented in [language-formatters-pre-commit-hooks](https://github.com/macisamuele/language-formatters-pre-commit-hooks)
+
 ## FAQ
 
 ### `ktfmt` vs `ktlint` vs IntelliJ