meta: add initial issue templates

This commit adds the following issue categories:
- Bug report
- Feature request
- Support

.github/ISSUE_TEMPLATE/support.md

@@ -0,0 +1,13 @@
+---
+name: Support
+about: Request support for any problem you're having with Oh My Zsh
+title: ''
+labels: 'Type: support'
+assignees: ''
+
+---
+
+<!--
+1. Try to make sure the issue is due to Oh My Zsh
+2. Include as much information as possible
+-->