Added theme update support

A major feature we felt was needed for our launch was automated theme updates to compliment the existing plugin update feature. We have made sure this feature works seamlessly and will now be included in v1 of the WP Git Updater tool!

Its also given us some great content to start building our blog section up: https://wpgitupdater.dev/blog/wp-git-updater-now-supports-theme-updates.