feat: add bun-fullstack agent and update skills

.agent/skills/tech-stack/elysiajs/examples/file.ts

@@ -0,0 +1,10 @@
+import { Elysia, file } from 'elysia'
+
+/**
+ * Example of handle single static file
+ *
+ * @see https://github.com/elysiajs/elysia-static
+ */
+new Elysia()
+	.get('/tako', file('./example/takodachi.png'))
+	.listen(3000)