chg: doc: [README.org] use public image in ``compose.yml`` and give more examples

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

README.org

@@ -119,19 +119,23 @@ the =-f COMPOSEFILE= option.  Here's a good start:
 cat <<EOF > compose.yml
 odoo:
   charm: odoo-tecnativa
-  # docker-compose:
-  #   ## Important to keep as a list: otherwise it'll overwrite charm's arguments.
+  docker-compose:
+    image: docker.0k.io/mirror/odoo:rc_13.0-MYC-INIT
+    ## Important to keep as a list: otherwise it'll overwrite charm's arguments.
     #command:
     #  - "--log-level=debug"
     #environment:
     #  TOTO: TATA
-  #   image: mynewimage
   #options:
   #  workers: 1
   #  modules:  ## 'base' is automatically added
   #    - l10n_fr
   #    - mymodule
   #  database: mybase  ## defaults to database in relation
+  #  ## Odoo configuration file
+  #  conf:
+  #    options:
+  #      email_from: me@example.com
 
 EOF
 #+END_SRC