Update: Implement @wordpress/html-entities package

[dinhtungdu]

Description of the Change

• Fixes Implement @wordpress/html-entities package #56, switch to the @wordpress/html-entities package to more fully resolve Unwanted html entity when sorting child pages #43 and see if that will avoid us getting dinged by automated scanners.
• Switch to webpack and to simplify our build configuration.
• Fixes Automate the build process #57 by removing built files from VCS and adding build command before publish to wordpress.org.

Verification Process

Manual verification.

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.

Changelog Entry

[dinhtungdu]

Closing this PR because it's out of date. This should be reworked in other PRs.