Import @ubiquity/ubiquibot event handler logic

[0x4007]

The GitHub event handler logic should be imported to this new codebase, and be sure to be compatible with Cloudflare Workers.

• No core node libraries like fs or path etc.
• I don't anticipate this to be a problem with the event handler code.

We can break this apart into several pull requests. I imagine that some will be basically copy and paste, while others may require some refactoring. Perhaps the first deliverable can be the easy ones, and we can work our way to the more complex refactorings.

[0x4007]

Probably a bad idea to rely on node polyfills but just wanted to leave this research here since it seems relevant in case of emergency https://developers.cloudflare.com/workers/wrangler/configuration/#add-polyfills-using-wrangler

[0x4007]

Let's not include any handlers in the kernel ubiquity/ubiquibot#906

[ubiquibot]

# Issue was not closed as completed. Skipping.