github: update issue templates

.github/ISSUE_TEMPLATE/misc.md

@@ -0,0 +1,16 @@
+---
+name: Misc
+about: Miscellaneous items you want to share
+title: "[misc]"
+labels: new
+assignees: ''
+
+---
+
+**Note**: for questions, please use the mailing-list: https://groups.google.com/g/mu-discuss
+
+**Describe the issue**
+A clear and concise description, i.e. what you expected/desired to happen and what actually happened.
+
+**Environment**
+If applicable, please describe the versions of OS, Emacs, mu etc. you are using.