feat: add bun-fullstack agent and update skills

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

@@ -0,0 +1,20 @@
+import { Elysia, t } from 'elysia'
+
+const app = new Elysia()
+	.post('/single', ({ body: { file } }) => file, {
+		body: t.Object({
+			file: t.File({
+				maxSize: '1m'
+			})
+		})
+	})
+	.post(
+		'/multiple',
+		({ body: { files } }) => files.reduce((a, b) => a + b.size, 0),
+		{
+			body: t.Object({
+				files: t.Files()
+			})
+		}
+	)
+	.listen(3000)