r/bitwarden_rs: Redirect to canonical host name

Bitwarden has not worked correctly for clients using the non-canonical
domain name (i.e. _bitwarden.pyrocufflink.blue_) for quite some time.
This still trips me up occasionally, though, so hopefully adding a
server-side redirect will help.  Eventually, I'll probably remove the
non-canonical name entirely.

roles/bitwarden_rs/defaults/main.yml

@@ -0,0 +1 @@
+bitwarden_domain: https://{{ bitwarden_host }}