Create Plugin: Introduce create plugin update workflow

[jackw]

What this PR does / why we need it: This PR adds a template file for running the create plugin update composite workflow and additional documentation to the website.

~Relies on grafana/plugin-actions/pull/38 being merged before this can be merged.~ The action is now merged.

Which issue(s) this PR fixes:

Fixes #818

Special notes for your reviewer:

📦 Published PR as canary version: Canary Versions

:sparkles: Test out this PR locally via: ```bash npm install @grafana/create-plugin@5.6.0-canary.1211.ec51a12.0 # or yarn add @grafana/create-plugin@5.6.0-canary.1211.ec51a12.0 ```

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[jackw]

Just an idea - would it make sense to add a note about the github token permissions into the print-success-message.ts?

I think that's a great idea @leventebalogh ! 🚀

[grafana-plugins-platform-bot[bot]]

:rocket: PR was released in @grafana/create-plugin@5.6.0, @grafana/plugin-e2e@1.9.0 :rocket:

[jackw]

I've opened #1241 for the success messaging @leventebalogh .