chore: add issue template

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,6 @@
+Please make sure these boxes are checked before submitting your issue. Thank you!
+
+- [] I have inited and configurated the blog according to [Hexo official documentation](https://hexo.io/);
+- [] I have read the [Theme Wiki](https://github.com/ppoffice/hexo-theme-icarus/wiki) carefully;
+- [] I have looked up the [Issues](https://github.com/ppoffice/hexo-theme-icarus/issues) and found no duplicate issues.
+