Add MPNGIN app

Adds a URL shortening utility used in production at https://express.mediaping.net

README.md

@@ -365,6 +365,7 @@ Contributions are welcome. Please take a quick look at the [contribution guideli
  * [lirith](https://github.com/lirith-engine/lirith) - Graphics engine
  * [m3u8](https://github.com/akiicat/m3u8) - Generate and parse m3u8 playlists for HTTP Live Streaming
  * [manual-generator](https://github.com/blocknotes/manual-generator) - Tool to generate PDF manuals from documentation sites
+ * [mpngin](https://github.com/thewalkingtoast/mpngin) - A URL shortener with simple stats
  * [raytracer](https://github.com/l3kn/raytracer) - CPU Raytracer with examples
  * [syscall.cr](https://github.com/kubo39/syscall.cr) - Raw syscall interface
  * [tren](https://github.com/sdogruyol/tren) - Give your SQL some love