Patch 9.2.0033 (#19260) introduced a dedicated `env` filetype for
.env files, which were previously detected as `sh`. This left env
files without `commentstring`, `comments`, or `formatoptions` since
no ftplugin was added alongside the new filetype.
Add runtime/ftplugin/env.vim to set these options, matching the
behavior that .env files had when they used the `sh` filetype.
closes: #19522
Signed-off-by: snelling-a <72226000+snelling-a@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
