More seamless sed / VIM Regex/Search Support

[Swivelgames]

It would be nice if sed/Vim regex support was a little more built-in to make the transition back and forth between Vim a little more seamless. It's a bit tough, though, because we likely don't want to transform Zed into Vim/Neovim, but personally I use sed search extensively in my day-to-day.

I recently enabled case-sensitive search by default.

	"search": {
		"case_sensitive": true
	},

But then I naturally used /\c to do a case-insensitive search, and realized I need to manually switch it to case-insensitive, which kind of broke me out of my trance 😅

I also noticed this when trying to use \v to enable regex replacing.

I don't know how deeply Zed desires to make the transition between Zed and Vim/Neovim seamless, but dedicated sed support would be great, specifically:

• Extending sed support to find, not just find/replace
• Improving sed support by toggling search features based on find flags (like \c, \C, \v, \V)
• Support for zero-width constructs (like \zs, \ze, etc...) (This might benefit from its own issue, honestly)