adding support for changing cursor in GNU screen

[rdyro]

Hi,

The purpose of this pull request is to allow zsh-vi-mode to change the cursor in the GNU screen.

The only change is wrapping the cursor style command in '\eP' '\e\' as detailed here:

• https://web.archive.org/web/20220411223346/https://ttssh2.osdn.jp/manual/4/en/usage/tips/vim.html#withScreen
• https://github.com/neovim/neovim/issues/17031

[rdyro]

After some more testing, highlighting (vim visual mode) does not appear to be working in GNU screen.

After some experimentation, I'm not sure how to fix this. The problem might be related to the zsh in-built region_highlight

I ended up switching from using GNU screen to tmux where everything works.

[jeffreytse]

everything

I think the tmux is a better alternative for your terminal experience. 👍