GitHub label functionality

[PI-Victor]

Context

The bot needs to respond to webhook events for PRs and add the corresponding labels to the PR.

Description

When opening a new PR, a webhook will fire to the endpoint specified in the wrangler.toml file, in turn, the bot will read the repo config and will add the labels to the PR the way that they are configured.

The functionality can be copied from the pre-existing Rust implementation: https://github.com/cloudflavor/oscar/blob/216190bd53d361de35f9f035adcd9b0c72bfbfc1/src/lib.rs

a rough sketch of the config is

Acceptance Criteria

• The bot reacts to webhook PR events for github (open, reopen, update)
• The bot reads the toml config in the root directory
• The bot adds the labels defined in the config to the PR

[linear]

CLO-36 GitHub label functionality

[PI-Victor]

ref: #11