Add/GitHub actions

[jeffpaul]

Description of the Change

Adds linting action, action to deploy new releases to WP.org, and action to deploy changes to readme.txt and/or assets to WP.org.

Alternate Designs

n/a

Benefits

automates plugin management tasks

Possible Drawbacks

Readme/asset changes only to trunk or doing a release will trigger the deploy actions, but both should fail with no match on the WP.org SVN side (for now).

Verification Process

Waiting for PR to run thru checks to see what needs to be fixed before this can be merged.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

n/a

Changelog Entry

### Added
- GitHub Actions (props @jeffpaul)

[dinhtungdu]

Linting actions are failing, we need to update the composer lock file and specify the JS folder.

[dinhtungdu]

The PHPCS job is failing due to the outdated composer.lock file, @jeffpaul can you please update it? After that, this is ready to be merged

[jeffpaul]

@dinhtungdu looks correct now, minus some actual PHPCS errors, yeah?

[jeffpaul]

Looks like those errors are all docs related, so I'm good merging this on and adding those in a subsequent PR.