Add vehicle selector and special notes for setup guide

[TheSecurityDev]

Add a vehicle selector to the setup guide, and a special notes card to dynamically show custom notes for specific models based on the setup_notes field on the data in vehicles.json.

Also does some refactoring and bug fixes to make this easier. For example, I had to refactor the harness selector to support only listing vehicles and not specific harnesses in some cases, since it doesn't make sense to show notes for a generic harness since there's no way to specify that in vehicles.json.

TODO:

• The custom notes only support HTML, not markdown. But this can probably be implemented easily with a third-party library if necessary.
• The custom notes will need to be created and added in opendbc, and then the vehicles_template.json can be modified accordingly.
• Replace some of the currently hardcoded custom notes (e.g. GM and Nissan)

[github-actions]

deployed preview: https://comma-web--pr25-3735muh5.web.app

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[TheSecurityDev]

Example note:

[TheSecurityDev]

Would this look better to have it horizontal in two columns? It seems like a lot of wasted space under the selector for larger notes though.

[TheSecurityDev]

If we had different setup videos available for each make (and model if necessary) we could put the embedded setup video on the right column.

[TheSecurityDev]

I'm not sure what else to do with this.