Update CONTRIBUTING.md

Co-authored-by: Daniël van Eeden <[email protected]>

Author: lance6716

CONTRIBUTING.md

@@ -7,7 +7,7 @@
   - What is the context? e.g. what versions of go-mysql, MySQL, etc does this apply to?
   - Do you have a simple test case? This can just be example code, it doesn't have to be a full test case.
   - Why do you need this change?
-- Format your code with [gofumpt](https://github.com/mvdan/gofumpt) if possible.
+- Format your code with [gofumpt](https://github.com/mvdan/gofumpt) if possible. (`make fmt` does this for you)
 - Reference an issue in the PR if you have one.
 - Update the `README.md` if applicable.
 - Add tests where applicable.