Escape [ and ] in hostname.
Escape [ and ] in hostname.

From URL:

    http://[fe80::cce4:1680:e720:eacb]:8080/index.html

generate:

    https?://\[fe80::cce4:1680:e720:eacb\]:8080/*

in the popup (note that [ and ] are now escaped).

Fixes #2967.

decaffeinate-examples/vimium,smblott-github/vimium,gdh1995/vimium,poacher2k/vimium,smblott-github/vimium,poacher2k/vimium,decaffeinate-examples/vimium,poacher2k/vimium,philc/vimium,philc/vimium,philc/vimium,decaffeinate-examples/vimium,gdh1995/vimium,gdh1995/vimium,smblott-github/vimium