Select more lines

Inspired by the Expand Line Selection (ctrl + l by default) of VSCode. It functions similarly to SelectLine, but if there's already a selection, the cursor select the next line. There's no default key binding, so you'll have to bind it yourself. For example:

{
    "Ctrl-l": "lua:selectMoreLines.selectMoreLines"
}

Note that I made this for personal use and I don't know what I'm doing.