It is very common to set `$EDITOR` to an terminal editor.
To do so, we have to attach the stdin and stdout to interact with it.
Otherwise the command would do nothing (when using `.Run()`) as it
silently fails or hang the command (using `.Start()`) because it waits
forever for input.
Also attaching stderr to make debugging easier if someone has a
non-compatible or broken `$EDITOR` set.
Reviewed-on: https://gitea.com/gitea/tea/pulls/706
Reviewed-by: Lunny Xiao <lunny@noreply.gitea.com>
Co-authored-by: Vincent Neubauer <v.neubauer@darlor.de>
Co-committed-by: Vincent Neubauer <v.neubauer@darlor.de>
