Add tmux config to allow neovim cursor shapes.
Add tmux config to allow neovim cursor shapes.

* Specifically, I want a thin cursor in insert mode, but a block cursor in normal mode.
* https://github.com/neovim/neovim/wiki/FAQ#cursor-shape-doesnt-change-in-tmux
* https://neovim.io/doc/user/term.html#tui-cursor-shape
* https://github.com/neovim/neovim/issues/4898
* https://github.com/neovim/neovim/pull/3165

joshukraine/dotfiles,joshukraine/dotfiles,joshukraine/dotfiles