chore: align Vue file conventions (#137)

- document Vue file authoring conventions
- rename runtime/example component files to kebab-case
- update imports and docs references

examples/flappy-bird/src/main.ts

@@ -5,6 +5,6 @@
 // Controls: space / ↑ / w to flap, q or Ctrl-C to quit, r to restart after dying.
 
 import { createApp } from "@vue-tui/runtime";
-import App from "./App.vue";
+import App from "./app.vue";
 
 createApp(App).mount();