Do not recommend select mode keybinds

[jemag]

Current README recommendation https://github.com/phaazon/hop.nvim/blob/master/README.md?plain=1#L149-L153 specifies keybind mode '', which includes select mode.

This means that Hop can be triggered in snippets. I believe most users would probably want to avoid using Hop in select mode, in this case the modes would be { "n", "x", "o" } instead

[hadronized]

Feel free to open a PR to fix it.