- Add a setting for `vertical_scroll_offset`
- Fix H/M/L in vim with scrolloff



Release Notes:

- Added a settings for `vertical_scroll_offset`
- vim: Fix H/M/L with various values of vertical_scroll_offset

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Co-authored-by: Vbhavsar <vbhavsar@gmail.com>
Co-authored-by: fdionisi <code@fdionisi.me>