feat: use vitest for testing

test/__snapshots__/component.test.ts.snap

@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Counter.vue > should render 1`] = `"<div>10 <button class=\\"inc\\"> + </button><button class=\\"dec\\"> - </button></div>"`;