Add railsbump

Author: asyraffff

README.md

@@ -607,6 +607,7 @@ Hey friend! Help me out for a couple of ☕️
     - [run.rb](https://github.com/jasoncharnes/run.rb) - Run Ruby in the browser using WebAssembly
   - **gems**
     - [decidim](https://github.com/decidim/decidim) - The participatory democracy framework. A generator and multiple gems made with Ruby on Rails 🔥 ✅ 🚀
+    - [railsbump](https://github.com/railsbump/app) - Check which gems are compatible with which Rails version! 🔥 ✅ 🚀
   - **Hosting**
     - [geminabox](https://github.com/geminabox/geminabox) - Really simple rubygem hosting 🔥 ✅ 🚀
   - **Interpreter**