[PR #3462/845c4064 backport][stable-3] Enable ansibullbot notifications in issues and PRs (#3465)

* Enable ansibullbot notifications in issues and PRs (#3462)

The more recent version of Ansibullbot defaults notifications to false.
We need to set it to true so it can notify contributors and maintainers.

(cherry picked from commit 845c406419)

* Update botmeta sanity test to accept notifications.

(cherry picked from commit 71a655193c)

Co-authored-by: David Moreau Simard <moi@dmsimard.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

.github/BOTMETA.yml

@@ -1,3 +1,4 @@
+notifications: true
 automerge: true
 files:
   plugins/:

tests/sanity/extra/botmeta.py

@@ -154,6 +154,7 @@ def main():
     }, extra=PREVENT_EXTRA)
 
     schema = Schema({
+        ('notifications'): bool,
         ('automerge'): bool,
         ('macros'): MacroSchema,
         ('files'): FilesSchema,