Establish basic file browser and index fallback (#2662)

Co-authored-by: L. Kärkkäinen <98187+Tronic@users.noreply.github.com>
Co-authored-by: L. Karkkainen <tronic@users.noreply.github.com>

sanic/base/root.py

@@ -9,6 +9,7 @@ from sanic.mixins.listeners import ListenerMixin
 from sanic.mixins.middleware import MiddlewareMixin
 from sanic.mixins.routes import RouteMixin
 from sanic.mixins.signals import SignalMixin
+from sanic.mixins.static import StaticMixin
 
 
 VALID_NAME = re.compile(r"^[a-zA-Z_][a-zA-Z0-9_\-]*$")
@@ -16,6 +17,7 @@ VALID_NAME = re.compile(r"^[a-zA-Z_][a-zA-Z0-9_\-]*$")
 
 class BaseSanic(
     RouteMixin,
+    StaticMixin,
     MiddlewareMixin,
     ListenerMixin,
     ExceptionMixin,