Add/GitHub actions

[jeffpaul]

Description of the Change

This PR adds the WordPress.org plugin deploy and WordPress.org asset/readme deploy GitHub Actions to help automate the release process and updating readme/assets on WordPress.org (useful for WordPress tested-up-to version bumps).

Alternate Designs

Keep as-is utilizing existing release/update processes.

Benefits

Eliminates human error during release process (assuming the actions are configured correctly).

Possible Drawbacks

Given this repo defaults to master instead of develop with releases merging from develop to master, then we'll see some of these actions firing more regularly as there will be more merges to master than are intended to trigger actions. An alternate scenario would be to create a develop branch, set that to default, and only merge to master when releasing a new plugin version (or bumping WordPress tested-up-to version).

Verification Process

Manually verified via the GitHub Desktop UI.

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

Inherits from #17.

Changelog Entry

### Added
- GitHub Actions for WordPress.org plugin and readme/asset deploys (props @jeffpaul)

[ChrisHardie]

@jeffpaul Thanks for setting this up. I believe you or someone at 10up will have to handle the final steps of populating the SVN creds and testing the action's first deploy, but let me know if there's anything else I can do here. I'm also fine with establishing develop as a branch for pushing works in progress before a release.

[jeffpaul]

@ChrisHardie I've added the SVN secrets to the repo, so good to merge this. Since you're mainly maintaining the plugin, happy to go with your preferred branches/branching process.

[jeffpaul]

@ChrisHardie so yeah looks like the 10up account may not have committer access to the SVN repo. We could swap in your credentials for the GitHub secrets, but probably better to add 10up as a committer on the SVN repo and the GitHub secrets as they are now will start working.

[ChrisHardie]

@jeffpaul Good catch, 10up is now a committer on the SVN repo.

[ChrisHardie]

Le sigh:

➤ Preparing files...
assets/banner-1544x500.png
assets/icon-256x256.png
assets/icon.svg
trunk/CHANGELOG.md
trunk/LICENSE
🛑 Other files have been modified; changes not deployed

[jeffpaul]

@ChrisHardie nope, that's expected as this PR changed more than just assets and/or the readme so the action should fail.