feat(nvim): add nvim package installer

[candrewlee14]

Testing on Linux worked. I'm currently unable to test on Windows due to #439.
This will resolve this feature request: webinstall/webi-installer-requests#30.

[candrewlee14]

Due to both inactivity & pain points when implementing my nvim package webinstall/webi-installer-requests#30, I decided to write my own cross-platform package manager called webman, inspired by webi. It handles package installation, removal, and switching all with a single yaml file per package.

I added neovim there if you find that helpful!

[coolaj86]

@candrewlee14 I happened across this today. I'll check out webman and see if I can glean any good ideas from it (I'd love to do a Webi 2.0 now that I've learned a lot more about the constraints of how the various packages need to be handled).

Non-commercial open source projects like this often benefit from a bump when you want to get something reviewed and it was missed.

If you could restore the branch that you created this from, I'd actually like to pull it in.