Add gem badge 💎 [ci skip]

sue445 · sue445 · commit 961fb31710ff · 2024-10-06T21:54:21.000+09:00
diff --git a/gem/README.md b/gem/README.md
@@ -1,6 +1,8 @@
 # GoGem
 Helpers for compiling Go extensions for ruby
 
+[![Gem Version](https://badge.fury.io/rb/go_gem.svg)](https://badge.fury.io/rb/go_gem)
+
 ## Installation
 Add below.
 
