Add rustfmt instructions to CONTRIBUTING.md

Author: tnull

CONTRIBUTING.md

@@ -120,7 +120,15 @@ Coding Conventions
 ------------------
 
 Use tabs. If you want to align lines, use spaces. Any desired alignment should
-display fine at any tab-length display setting.
+display fine at any tab-length display setting. We use `rustfmt` to establish
+uniform coding standards throughout the codebase. Please run
+
+```bash
+./ci/rustfmt.sh
+```
+
+before committing and pushing any changes, as compliance will also be checked
+and enforced by our CI scripts.
 
 Our CI enforces [clippy's](https://github.com/rust-lang/rust-clippy) default
 linting