Update issue templates

Author: tuoping

.github/ISSUE_TEMPLATE/about-input-files.md

@@ -0,0 +1,21 @@
+---
+name: Request for Help
+about: Don't post help requests here, go to [discussions](https://github.com/deepmodeling/deepmd-kit/discussions)
+  instead.
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+Before asking questions, you can
+
+search the previous issues or discussions
+check the [document](https://deepmd.readthedocs.io/en/stable), especially [training parameters](https://deepmd.readthedocs.io/en/stable/train-input.html).
+
+Please **do not** post requests for help (e.g. with installing or using deepmd-kit) here. 
+Instead go to [discussions](https://github.com/deepmodeling/deepmd-kit/discussions).
+
+This issue tracker is for tracking deepmd-kit development related issues only.
+
+Thanks for your cooperation.