Add Tier 1 description features

[jessegreenberg]

In #101 it was decided that we are going to try to add Tier 1 description for trig-tour. That includes

• Accessible names for interactive components
• Help Text for interactive components
• Screen summaries

[jessegreenberg]

I will take a first pass at this to set up the boilerplate then assign to the design team for content.

[jessegreenberg]

OK, the basics are in place as placeholders. Some but not all components are getting the names from the visual text. The a11y view looks something like this:

If that is not helpful or difficult to read let me know and I won't do this again. But I thought this might be helpful as a starting point.

@amanda-phet can you please let me know what content you would like in here? Or feel free to edit https://github.com/phetsims/trig-tour/blob/main/trig-tour-strings_en.json directly. Let me know if optional help text should be deleted or if I missed anything.