docs(@angular/build): include component templates in dev-server hmr description

The `hmr` option description stated that only global and component stylesheets
are supported. Component template hot replacement is also enabled by default when
HMR is active, so list templates alongside the supported stylesheets.

Author: MeAkib

packages/angular/build/src/builders/dev-server/schema.json

@@ -91,7 +91,7 @@
     },
     "hmr": {
       "type": "boolean",
-      "description": "Enable hot module replacement. Defaults to the value of 'liveReload'. Currently, only global and component stylesheets are supported."
+      "description": "Enable hot module replacement. Defaults to the value of 'liveReload'. Currently, global stylesheets, component stylesheets, and component templates are supported."
     },
     "watch": {
       "type": "boolean",