Add instructions for how to run locally

[achou11]

Notably:

• General dev flow (e.g. live server, which port to use, etc)
• Setting up the Earthstar config stuff using https://github.com/earthstar-project/applet-control-panel

[johanbove]

Perhaps also add to the workshop where the earthstar.bundle.js file came from?

[achou11]

Perhaps also add to the workshop where the earthstar.bundle.js file came from?

ah yeah that too, although at the moment, gwil just custom bundled it and shared the file directly with me 😄 for now, the instruction would be to just copy+paste the file I have in the repo