feature/viewport button component

Time to review:

Medium Design review with UX complete.

Problem

Viewport buttons (camera and playback controls) do not match current style guidance. The code for these buttons and their stylesheets is not DRY.

Solution

Create ViewportButton component. Each ViewportButton wraps a button in a tooltip and takes a short list of custom props that get it styled correctly. Implementing components (playback controls, camera controls, forthcoming record movies component) are concise and readable.

Relevant re-organizing and re-naming is ongoing in colors.css. It's a pain, but if any reviewers would like to use it I have a python script that scans the repo for unused css vars and css properties that use variables that aren't actually defined (there were several!) that is making this somewhat less painful T_T

Bug fix (non-breaking change which fixes an issue) (style issues)
New feature (non-breaking change which adds functionality) (wrapper component)

Steps to Verify:

Confirm styling is correct for buttons in default, hover, and active states.

Screenshots (optional):

Old:

New:

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🟡	Branches	68.38%	80/117
🔴	Functions	40.31%	79/196
🟡	Lines	71.73%	538/750

simularium / simularium-website