docs: add deno badge to show deno version to support

Author: lambdalisue

README.md

@@ -1,6 +1,7 @@
 # 🍂 fall-std
 
 [![JSR](https://jsr.io/badges/@vim-fall/std)](https://jsr.io/@vim-fall/std)
+[![Deno](https://img.shields.io/badge/Deno%202.x-333?logo=deno&logoColor=fff)](#)
 [![Test](https://github.com/vim-fall/fall-std/actions/workflows/test.yml/badge.svg)](https://github.com/vim-fall/fall-std/actions/workflows/test.yml)
 [![codecov](https://codecov.io/gh/vim-fall/fall-std/graph/badge.svg?token=FWTFEJT1X1)](https://codecov.io/gh/vim-fall/fall-std)
 [![MIT License](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE)