Apply layout and design to YouTube video transcript annotation interface

[lyzadanger]

This work pertains to the video-annotation interface (in via).

This work includes, but is not limited to:

• basic layout and dimensions for baseline (i.e. desktop) viewport
• adjustment of transcript (entries, spacing, typography, etc.)
• adjustment of toolbar, buttons, and actions
• alignment, both vertical and horizontal, of transcript with sidebar
• branding
• adjustments of scrolling and alignment per bucket bar
• layout at different viewport sizes (breakpoints) (first pass only; iteration will be tracked separately)
• error and messaging styling (potentially with toast messaging) Tracked separately

This work is done when we have had a design review and revisions can be tracked separately.

Separately-tracked and follow-up issues directly related to this theme (not exhaustive)

• Figure out what to do with the "Auto-scroll" control (design)
• Show sidebar alongside transcript #954
• Add a toast message component for use in video-annotations application (errors)

[lyzadanger]

The initially-tracked tasks in this ticket have been completed, and all remaining design tasks are tracked in separate issues.