search: Mark App.vue as being compatible with Vue 3

This doesn't change any behavior, it just suppresses a compatibility
warning and ensures that future changes to this file won't introduce
code that relies on Vue 2 compatibility features.

Change-Id: Id15af7d5d5035f59dc8f402f00d8f7f0d73a77f7

resources/skins.vector.search/App.vue

@@ -51,6 +51,12 @@ const { CdxTypeaheadSearch } = require( '@wikimedia/codex-search' ),
 // @vue/component
 module.exports = exports = defineComponent( {
 	name: 'App',
+	compatConfig: {
+		MODE: 3
+	},
+	compilerOptions: {
+		whitespace: 'condense'
+	},
 	components: { CdxTypeaheadSearch },
 	props: {
 		id: {