Convert issue templates to issue forms.

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -0,0 +1,33 @@
+name: Feature Request (Traefik)
+description: Suggest an idea for this project.
+body:
+  - type: checkboxes
+    id: terms
+    attributes:
+      label: Welcome!
+      description: |
+        The issue tracker is for reporting bugs and feature requests only. For end-user related support questions, please refer to one of the following:
+        - the Traefik community forum: https://community.containo.us/
+
+        DO NOT FILE ISSUES FOR GENERAL SUPPORT QUESTIONS.
+      options:
+        - label: Yes, I've searched similar issues on [GitHub](https://github.com/traefik/traefik/issues) and didn't find any.
+          required: true
+        - label: Yes, I've searched similar issues on the [Traefik community forum](https://community.containo.us) and didn't find any.
+          required: true
+
+  - type: textarea
+    attributes:
+      label: What did you expect to see?
+      description: |
+        How to write a good issue?
+
+        - Respect the issue template as much as possible.
+        - The title should be short and descriptive.
+        - Explain the conditions which led you to report this issue: the context.
+        - The context should lead to something, an idea or a problem that you’re facing.
+        - Remain clear and concise.
+        - Format your messages to help the reader focus on what matters and understand the structure of your message, use [Markdown syntax](https://help.github.com/articles/github-flavored-markdown)
+      placeholder: What did you expect to see?
+    validations:
+      required: true