Improve technical documentation for description features.

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Related to https://github.com/phetsims/special-ops/issues/269 ...

There are some existing documents that are a nice start on describing the technical aspects of description in PhET sims, how to implement, etc. For example the various binder (.md) files and the interactive-description-technical-guide.md.

But in speaking with various developers during https://github.com/phetsims/special-ops/issues/269, there was a universal theme -- developers are not finding the information that they need in the documentation that currently exists.

• Identify what developers need when implementing sims.
• Identify what developers need when implementing reusable UI components (which if likely different than for sims)
• Identify and document implementation patterns.
• Provide concise quickstart guides for "tiers" of description -- for example, a quickstart guide of acessible names and help text. Quickstart guides are a very useful entry point, and especially useful as something to come back to for a refresher.
• Build out more binder files. Identify what developers and designers need in these files.
• Create all documentation with SceneryStack/POSE in mind.

... and there are undoubtedly other needs to consider, to be discovered during discussion.