Add support for marks

[jssee]

It would be nice to have something like [m and ]m for cycling through marks in a buffer, and perhaps capital M variants too.

[iforwms]

These are already bound by default in vim.

[m / [M | Jump to beginning/end next of method ]m / ]M | Jump to beginning/end of previous method

[tpope]

More generally, the number of remaining free maps is small, and thus the value of any new ones I'm willing to consider must be extremely high. I don't think mark cycling makes the cut. It's not even clear to me which set of marks to include.

• The letter marks? Feels low value. If you went to the trouble of assigning a letter you'd probably be better served by just jumping to it directly.
• The weird ones like [' and [^? I think this would be confusing without a companion plugin like ShowMarks to see where you'd jump to. And if you do have a companion plugin installed, that plugin would be in a much better position to provide such maps.