add webi install method

[coolaj86]

So it looks like you are the author of at least three tools that I love. I see @ErichDonGubler is a contributor here is well. Yay!

I've added hexyl, bat, and fd to https://webinstall.dev, all based on the same installer template - except no Windows 10 for hexyl :'(

In short, webi

• pulls your official builds from the Github Release API
  • (selecting a build that it can unpack with whatever tools are available no the system in question - tar, zip, etc
• places it in ~/.local/opt/<whatever>-<version>
• creates a symlink to ~/.local/bin/<whatever>
• updates PATH in ~/.config/envman/PATH.env

No sudo. No package manager. No nonsense.

• Installer source at https://github.com/webinstall/packages/blob/master/hexyl/

[sharkdp]

see https://github.com/sharkdp/bat/pull/1105