Checkvist extended commands

# What

It adds four new commands to Checkvist (https://checkvist.com)

Commands:

l - Expand node (same as `→`)
L - Focus the list item (same as `Shift →`)
h - Collapse node (same as `←`)
H - Un-focus the list item (same as `Shift ←`)
o - Add below (same as `enter`)
O - Add above (same as `alt+enter`)
G - Go to the last item in the tree (same as `End` or `Fn+Down`)
alt+g alt+g - Go to the first item in the tree (same as `Home` or `Fn+Up`)
meta+j - macOS users: Move list items down (same as `⌘ ↓`)
meta+k - macOS users: Move list items up (same as `⌘ ↑`)

You can find the code at https://github.com/NicoSantangelo/checkvist-extended-commands