Add composer autoload

[MaxwellGarceau]

Description of the Change

Added autoloading to have an easy way to modularize new code and refactor existing code in the future.

❗I modified the Github action workflow files to install composer dependencies in order to ensure autoload was being generated on every build. I wanted to flag this in case I missed a required build process update.

Also, if there's a good place to add documentation for in progress pattern updates I'd be happy to add switching to autoload in new work and any refactors.

Closes #96

How to test the Change

Changelog Entry

Added - New feature
Changed - Existing functionality
Deprecated - Soon-to-be removed feature
Removed - Feature
Fixed - Bug fix
Security - Vulnerability

Credits

Props @username, @username2, ...

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[dkotter]

Overall this looks good but we'll need to do a few more things:

1. We have a GitHub Action that deploys plugin assets and readme changes. That will need to be updated to run composer install as well
2. We don't currently deploy the vendor directory so we'll need to update that or things won't work in the final release. We have both a .distignore and .gitattributes files that will need updated

[MaxwellGarceau]

Overall this looks good but we'll need to do a few more things:

1. We have a GitHub Action that deploys plugin assets and readme changes. That will need to be updated to run composer install as well
2. We don't currently deploy the vendor directory so we'll need to update that or things won't work in the final release. We have both a .distignore and .gitattributes files that will need updated

@dkotter I've made the requested changes.

1. Updated .github/workflows/wordpress-plugin-asset-update.yml with the composer install and autodump commands
2. Removed the vendor folder from distignore and gitattributes

Note: I've updated the translators comment to match an example I found in WP Core.