Watch for changes to the template file during documentation serve (#9244)

Fixes this really annoying behavior where the served documentation would
not reflect changes to the mkdocs template file (where we store all of
our actual configuration)

ref https://github.com/mkdocs/mkdocs/pull/2642

mkdocs.insiders.yml

@@ -1 +1,4 @@
 INHERIT: mkdocs.template.yml
+
+watch:
+  - mkdocs.template.yml

mkdocs.public.yml

@@ -4,3 +4,5 @@ plugins:
   - search
 validation:
   anchors: warn
+watch:
+  - mkdocs.template.yml