Add links to README badges (#80)

README.md

@@ -1,15 +1,16 @@
 # Among Us for Garry's Mod
 
-[![Discord](https://img.shields.io/discord/784594024644083735?color=7289DA&label=chat&logo=discord)](https://discord.gg/4A5ekSuGeq)
+[![Discord](https://img.shields.io/discord/784594024644083735?color=7289DA&label=chat&logo=discord)][discord-invite]
 
-![Steam Subscriptions](https://img.shields.io/steam/subscriptions/2308955070?logo=steam)
-![Steam Favorites](https://img.shields.io/steam/favorites/2308955070?logo=steam)
-![Steam Update Date](https://img.shields.io/steam/update-date/2308955070?label=last%20updated&logo=steam)
-
-[Steam Workshop](https://steamcommunity.com/sharedfiles/filedetails/?id=2308955070)
+[![Steam Subscriptions](https://img.shields.io/steam/subscriptions/2308955070?logo=steam)][steam-workshop]
+[![Steam Favorites](https://img.shields.io/steam/favorites/2308955070?logo=steam)][steam-workshop]
+[![Steam Update Date](https://img.shields.io/steam/update-date/2308955070?label=last%20updated&logo=steam)][steam-workshop]
 
 This project aims to re-create [Among Us](http://www.innersloth.com/gameAmongUs.php), a game by InnerSloth, in [Garry's Mod](https://store.steampowered.com/app/4000/Garrys_Mod/).
 
+[discord-invite]: https://discord.gg/4A5ekSuGeq
+[steam-workshop]: https://steamcommunity.com/sharedfiles/filedetails/?id=2308955070
+
 ## Preparing the Environment
 
 This project is built using Gulp. To get started, you will need to install Node.JS 13.0.0+.