Make an additional COLLAPSE option for video descriptions

⚬ PROBLEM: The summary (name for the first 3 lines of video's description) can be useful but distracting sometimes. The "hidden" option hides it completely without a "show more" text button, so I have to re-enable it and remember to disable it every time to avoid possible one-liner distractions in the future.

⚬ SOLUTION: Just like there's an "EXPAND" option, add a "COLLAPSE". This way, the description (including the summary) will be hidden under a "show more" text button, and if clicked, it'll expand completely.

⚬ ALTERNATIVES: Make the "show less" text button appear always at the top (basically in place of "show more"), so it can be dismissed without scrolling to the bottom (which allows room to read distracting paragraphs, symbols, ads and links).

⚬ RELEVANCE / SCOPE: Definitively. As you watch or listen to videos, it encourages reading only when context demands it: allows room to think why do you need to read it in the first place. Not having this feature? chances are, even one word can be distracting, it even makes you want to comment something right after reading, eg. puns (and then you get distracted by the comments... you get the picture).

⚬ "SIDE EFFECTS": I have none at the moment.

No files, tests, or entry points are named. Start by locating the existing EXPAND and hidden description options in the extension, then trace how the description controls are rendered and persisted. Done means a COLLAPSE option hides the summary behind a “show more” control and expands the full description when selected.