Improve the interaction for 'viewed files' in the Changes View

[egamma]

Toggling the viewed state for a file in the Changes view is not intuitive:

After clicking the 'checked' inline action, the toggle action moves around and is replaced with very different icon.

[miguelsolorio]

Also worth pointing out that we use a mixture of checks, would be nice to consolidate/make it a bit more consistent:

[lychung7]

Below we changed the toggle icons to checks and filled checks, and we also introduced color state changes. For accessibility reasons and for those who have colors turned off, we kept the check label next to the Modified label. To address Miguel's point on consistency, we are using the same check as the one in front of the pull request name in the screenshot he shared.

Screen.Recording.2022-02-15.at.8.46.21.AM.mov

[miguelsolorio]

Love how clear the checks are, it would be nice if the position of the icons could stay the same so it could be an easy "toggle" which makes me wonder if we can find a decorator for "not yet reviewed" so the position stays consistent?

[alexr00]

What if we swap the "git" decoration (M, D, A, etc.) for the check?

I've also changed the order of the buttons so that the "mark as viewed" button is closer to the decoration that changes.

[lychung7]

@misolori we had also explored an indicator next to the file name for when the file hasn't been marked as viewed yet. Although the dot is used in other scenarios in list views. I think what @alexr00 suggested for swapping could also be a good idea! Users might not need to see the git decorations after they mark them as viewed.

Screen.Recording.2022-02-16.at.7.51.27.AM.mov