Exclude vendor library and POT file

[dinhtungdu]

Description of the Change

Remove pot file and vendor library from git. Update the release workflow to build the language file and install composer packages on release.

Alternate Designs

N/A

Benefits

Cleaner code base.

Possible Drawbacks

N/A

Verification Process

Check the stable branch after running updated release workflow to see language file and plugin-update-checker library.

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

Fixes #64

Changelog Entry

N/A

[jeffpaul]

We may want to look at bumping the update checker to its latest v4.10 as well as possibly leveraging https://github.com/Automattic/jetpack-autoloader to help with conflicts with other plugins using the same update checker but different version (e.g., https://github.com/10up/10up-experience). Punting this to 1.7.0 to allow for more time to work on this while we in parallel work to releasing 1.6.0.

[jeffpaul]

Note that this will likely mean updates to the release instructions in CONTRIBUTING.md as well the 1.7.0 release issue steps.

[iamdharmesh]

LGTM! Thanks for the PR @dinhtungdu

[dinhtungdu]

Note that this will likely mean updates to the release instructions in CONTRIBUTING.md as well the #289.

@jeffpaul I updated the release instruction per your suggestion.