[Maker] Add micro:bit category to Droplet toolbox

[ajpal]

1. Renames the experiment from bett-demo to microbit
2. Adds the micro:bit blocks to the droplet config
3. Shows the Maker and micro:bit categories if the experiment is enabled. Shows the Maker and Circuit categories if the experiment is not enabled.
   Future work- detect which kind of board is plugged in to determine which category to show.

With Experiment:

Maker Category:

micro:bit Category:

Without Experiment:

Links

• spec
• STAR-646
• STAR-647

Testing story

Reviewer Checklist:

• Tests provide adequate coverage
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[jmkulwik]

This all looks good to me. Do you want us to test it out before you merge?