More navigation keybindings for confirmation panel

[stefanhaller]

• PR Description

Add bindings for , (page up), . (page down), < or <home> (top), and > or <end> (bottom), for scrolling long text in confirmation panels. This is useful for example for git hooks that output a lot of error text on failure, where the most interesting bit of information is probably at the end.

I chose not to bind <pgUp> and <pgDown>, since they are normally used for scrolling the main view. Which is not a thing when a confirmation is shown or the Extras panel is focused, so we could use them in these cases, but I thought it might be confusing when they are used for different things in different contexts.

While we're at it, add the same navigation bindings also to the Extras panel (i.e. the command log when it has the focus).

Fixes #4372.

• Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for ed0cc8b1	✅ 56.25%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (ed0cc8b)	Report Missing	Report Missing	Report Missing
Head commit (8a45060)	54015	46798	86.64%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#4404)	128	72	56.25%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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Footnotes

1. Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct. ↩

[jesseduffield]

LGTM