Add some vim "z" keybindings for scrolling

[syndesis]

Release Notes:

• Added a few "z" keybindings from vim for scrolling

[cla-bot[bot]]

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[syndesis]

@cla-bot check

[cla-bot[bot]]

The cla-bot has been summoned, and re-checked this pull request!

[mrnugget]

Thanks!