feat: Add custom JS file and vim keybinding functionality

[jackgdn]

Pull Request type

Please check the type of change your PR introduces:

• Bug-fix
• Feature (functionality, design, translations, etc.)
• Documentation change
• Project management (tests, CI, GitHub configuration, etc.)
• Other (please describe):

Current state

Issue Number(s):

Proposed changes

Key	Function
gg	Go to the top
Shift + G	Go to the bottom
/	Search
j	Scroll half a page up
k	Scroll half a page down
Shift + N	Toggle display mode

Screenshots, if applicable

Checklist

• Bug-fixes and new features: I have tested locally with the latest release of Hugo extended. This requirement is a standard.
• Bug-fixes, new features, and doc changes: I have updated the relevant documentation as part of this PR.
• All PRs: I have signed off (using git commit -s ...), or if not possible due to developer environment constraints, will comment below confirming that I am adhering to the Developer Certificate of Origin.

[chipzoller]

Seeing a failure here in CI, not sure if related. @jackgdn, please sign-off on your commits per DCO.