Add missing Minecraft versions to issue template

Author: DerEchtePilz

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -20,6 +20,8 @@ body:
       description: What version of Minecraft are you using? _(If using a minor version that isn't specified, such as 1.18.1, just select the latest version below it such as 1.18)_
       multiple: false
       options:
+        - "1.21"
+        - "1.20.6"
         - "1.20.5"
         - "1.20.4"
         - "1.20.3"