Changes from PHP:
- Form action now points to `/pkgbase/{name}/comaintainers`.
- When an error occurs, users are sent back to
`/pkgbase/{name}/comaintainers` with an error at the top of the page.
(PHP used to send people to /pkgbase/, which ended up at a blank
search page).
Closes: https://gitlab.archlinux.org/archlinux/aurweb/-/issues/51
Signed-off-by: Kevin Morris <kevr@0cost.org>
