views: Add footer to StreamsView and TopicsView

[plugyawn]

What does this PR do?
Added the shortcut hint for displaying Topics to the Streams Panel and a hint to get back to Streams in the Topics Panel.

Associated with #1190. Discussed on CZO at Stream/topic toggle hint?

Tested?

• Manually
• Existing tests (adapted, if necessary)
• New tests added (for any new behavior)
• Passed linting & tests (each commit)

Commit flow

• first commit adds the footer for the hints.
• upcoming commit will add functionality for hint to only appear when cursor is in the panel.

Notes & Questions

• Still shows hint even when not in the left panel, causing probable misunderstanding about where one has to press t, so have to fix that.

Visual changes

[neiljp]

@plugyawn Thanks for exploring this 👍 See my thoughts in the stream, since this is mainly visual so we may want to discuss rather than focus on implementation.

[plugyawn]

@neiljp implemented the theming change. Is it clearer to look at now?

[plugyawn]

@zulipbot add "PR needs review"

[neiljp]

Feedback was given in the stream.

[neiljp]

@plugyawn You didn't change the labels on this, though have pushed since we last reviewed. I left a note in the stream.

[plugyawn]

@plugyawn You didn't change the labels on this, though have pushed since we last reviewed. I left a note in the stream.

Oh, I just fixed the commit text for the PR, didn't add anything new, so I didn't change the labels.

[zulipbot]

Heads up @plugyawn, we just merged some commits that conflict with the changes you made in this pull request! You can review this repository's recent commits to see where the conflicts occur. Please rebase your feature branch against the upstream/main branch and resolve your pull request's merge conflicts accordingly.