fromSb3: Fix loading component-based pen color blocks; document shadow blocks' fields more carefully

[towerofnix]

Development:

• Resolves fromSb3: Peculiarity with pen_menu_colorParam as shadow input (etc?) #144
• Towards Cannot read properties of undefined (reading 'opcode') #141 (specific project)

Hard-codes(!) a special-case fix for the pen_menu_colorParam shadow block; we reviewed all shadow blocks that Leopard supports and would have included like fixes for any similar cases, but this is the only one.

pen_menu_colorParam is different from normal SB3 shadow blocks because its field is named colorParam and does not match the name, COLOR_PARAM, of the input into which it is placed. All other names do match and we can just apply the shadow block's field as an sb-edit input with the same name, but this one needs to be manually transferred from sb3 field colorParam to sb-edit input COLOR_PARAM.

This fixes loading blocks which use this input (there are two in the Pen extension) and makes it so output formats see the COLOR_PARAM input that they're expecting. Our testing:

• Manually tested with project Set/change pen (color...) menu tests
• Manually tested with project WebOMatic!
• Both toLeopard and toSb3 are working, and don't require any changes.
  • Included reviewing generated project.json for first project, see: fromSb3: Peculiarity with pen_menu_colorParam as shadow input (etc?) #144 (comment)
  • Not directly related, but Leopard's component-based pen color does work with these blocks correctly!
• Updated snapshot test (which loads with fromSb3 and writes with toLeopard,toSb3, and toScratchblocks)
  • Internal project.json is now pretty-printed w/ JSON.stringify for more convenient git review. The SB3 is very old and saving it from the Scratch editor without making any changes will still produce a flat-out different file (in subtle ways), so the diff was manually reviewed to only commit the code changes. This should make for a clean diff in the snapshot file.

[towerofnix]

Have requested a review from @adroitwhiz since this is probably at least of note to you, but all cool if you aren't around to look at this closely at the moment!

[adroitwhiz]

LGTM! At some point, it may be worth revisiting shadow blocks but this should fix things for now.