docs: update release process (#3032)

* docs: edit changelog

* Update CONTRIBUTING.md

Co-authored-by: Keeley Hammond <khammond@slack-corp.com>

Co-authored-by: Keeley Hammond <khammond@slack-corp.com>

CONTRIBUTING.md

@@ -119,6 +119,7 @@ bolt upgrade electron-wix-msi@latest
   - This will commit the changes automatically. Run `git log` to confirm that the changes have been
     committed.
   - `$NEW_VERSION` should be an un-prefixed [semantic version](https://semver.org/) number (e.g. `6.0.0-beta.67)
+- Run `git clean -fdx` - this will ensure unneeded build files (and potentially sensitive files) are not included in the npm package.
 - `$ node tools/publish.js`
   - Ensure that you are logged into npm via command line (`npm login`)
 - After running the command, you should have a commit which: