Enable user-configurable probes on Helm Chart for streaming and web

[jstewart612]

Pitch

I'd like to be able to, using the first-party Mastodon Helm Chart, configure my liveness, readiness, and startup probes on Deployment objects to meet my needs of my running environment.

Motivation

People who want to either do more advanced probes and checking for health, or users who want to customize probes to operate Mastodon in slower environments are two examples that immediately spring to mind.

[jstewart612]

As per @Gargron on the PR, closing in favor of mastodon/chart#9 . The helm chart in this repository really should be cleaned up and all links pointed there, but that's a separate issue IMO than this so closing this.