update contributing guidleines on force pushing (#1468)

Author: anthony-gomez-fastly

CONTRIBUTING.md

@@ -5,16 +5,17 @@ please open an [issue](https://github.com/fastly/cli/issues/new) to discuss the
 idea and implementation strategy before submitting a PR.
 
 1. Fork the repository.
-1. Create an `upstream` remote.
+2. Create an `upstream` remote.
 ```bash
 $ git remote add upstream git@github.com:fastly/cli.git
 ```
-1. Create a feature branch.
-1. Write tests.
-1. Validate and prepare your change.
+3. Create a feature branch.
+4. Write tests.
+5. Validate and prepare your change.
 ```bash
 $ make all
 ```
-1. Add your changes to `CHANGELOG.md` in [Commitizen](https://commitizen-tools.github.io/commitizen/) style message
-1. Open a pull request against `upstream main`.
-1. Celebrate :tada:!
+6. Add your changes to `CHANGELOG.md` in [Commitizen](https://commitizen-tools.github.io/commitizen/) style message
+7. Open a pull request against `upstream main`.
+        1. Once you have marked your PR as `Ready for Review` please do not force push to the branch
+8. Celebrate :tada:!