Match animated emojis

Created by: VelvetThePanda

Make sure you familiarize yourself with our contributing guidelines.

Summary

Your regex was :b:orked

Details

I don't know what they're used for, but I noticed regexes that matched emojis don't match animated emojis which have the structure of <a:name:id> where regular emojis do not have the a there.

Changes proposed

Added a? to appropriate regexes in Utilities.cs

Notes

I totally understand if this gets shot down for being a micro-pr; I was browsing through code while looking for something else and noticed this. Kinda bugged me.