Add support for adding comments to the subjects

[hudson-newey]

Users have expressed the desire to add comments (freeform text) to the subjects so that they can add additional context as to why they made a decision.

Alternative:
We might be able to send them to the existing listen page instead of adding this functionality directly to the verification grid

[atruskie]

So this is a a so called refinement and is in the same category as annotation editing.

[atruskie]

Oh, and we also want to not encourage comments - it tends to be a crutch for an interface that is not powerful enough to descriptively label their dataset. It also slows down the ideally fast verification process we're trying to set up.

That being said, one cannot anticipate every situation, so an escape hatch still holds value.

If added: maybe an option to enable, and maybe a comment icon on each tile.

[nellihol]

I suggest adding a "add note" button between the play and settings buttons to allow users to add spectrogram-specific notes. This button icon could be a speech bubble (for comment) or a post-it note with a plus icon.

This could be a setting on #178

Examples: