Merge pull request #5814 from poulad/update-contrib

docs(core): edit contribution guide

CONTRIBUTING.md

@@ -249,14 +249,16 @@ If the commit reverts a previous commit, it should begin with `revert:`, followe
 Must be one of the following:
 
 - **build**: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
+- **chore**: Updating tasks etc; no production code change
 - **ci**: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
 - **docs**: Documentation only changes
-- **feature**: A new feature
+- **feat**: A new feature
 - **fix**: A bug fix
 - **perf**: A code change that improves performance
 - **refactor**: A code change that neither fixes a bug nor adds a feature
 - **style**: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
 - **test**: Adding missing tests or correcting existing tests
+- **sample**: A change to the samples
 
 ### Scope