Move ISSUE_TEMPLATE (#1567)

This PR moves the `ISSUE_TEMPLATE` to the root and removes the old ones.

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -0,0 +1,35 @@
+name: Bug Report
+description: Let us know about an issue you experienced with this software
+labels: [ I2-bug, I10-unconfirmed ]
+
+body:
+  - type: checkboxes
+    attributes:
+      label: Is there an existing issue?
+      description: Please search to see if an issue already exists and leave a comment that you also experienced this issue or add your specifics that are related to an existing issue.
+      options:
+        - label: I have searched the existing issues
+          required: true
+  - type: checkboxes
+    attributes:
+      label: Experiencing problems? Have you tried our Stack Exchange first?
+      description: Please search <https://substrate.stackexchange.com> to see if an post already exists, and ask if not. Please do not file support issues here.
+      options:
+        - label: This is not a support question.
+          required: true
+  - type: textarea
+    id: bug
+    attributes:
+      label: Description of bug
+      description: What seems to be the problem?
+      # placeholder: Describe the problem.
+    validations:
+      required: true
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to reproduce
+      description: Provide the steps that led to the discovery of the issue.
+      # placeholder: Describe what you were doing so we can reproduce the problem.
+    validations:
+      required: false