Make it easier to automatically populate one or more layouts into web version of Studio, auto-connect to data source

[jhurliman]

Use case: I have a robot that is sometimes Internet-denied, and I want to use Foxglove Studio as the UI into this robot. I have one or more layouts that I have created specifically tailored to this robot and exported as JSON. I want to host the web version of Studio running on my robot, and when anyone visits https://myrobot.local/ Studio loads with one of my layouts and automatically connects to my robot's data source (for example rosbridge at wss://myrobot.local:9090). Optionally, other layouts are available to switch to as well.

Under the hood this could be implemented with a redirect from https://myrobot.local/ to https://myrobot.local/foxglove/?layout_url=...&data_source=... or something to that effect.

[RFRIEDM-Trimble]

This could serve as a nice workaround in our use case to #148 that prevents our users from uploading layouts. If it's already on the robot (through other means), no need to upload anything.

[amacneil]

Making a note that the best workaround for this today is to build your own local copy of studio, and edit the default layout:

https://github.com/foxglove/studio/blob/main/packages/studio-base/src/providers/CurrentLayoutProvider/defaultLayout.ts

I agree that it would be nice to support this directly rather than requiring you to recompile the app.