Consider moving MoleculesAndLightKeyboardHelpContent to this repo and renaming

[jbphet]

As of this writing, the keyboard help dialog for the Molecules and Light sim is in the molecules-and-light repo, but most of the rest of the code for that sim is in this repo (greenhouse-effect) because the planned "Micro" screen of the Greenhouse Effect sim will share most of its code with Molecules and Light. However, the design of the "Micro" screen is not complete and has been paused, and according to @kathy-phet isn't likely to get any attention soon. So, at this point, it's impossible to say whether the keyboard help dialogs for the two sims can be the same, slightly different (which could potentially be handled through parameterization), or different enough that each repo should have its own version. Once work on the "Micro" screen resumes, we should sort this out.

[jbphet]

Deferring until work on the "Micro" screen resumes.