CI: more updates to feature request template (#16531)

More updates

.github/DISCUSSION_TEMPLATE/ideas.yml

@@ -6,9 +6,11 @@ body:
       label: Checked
       description: Please confirm and check all the following options.
       options:
-        - label: I searched existing ideas and did not find a similar one.
+        - label: I searched existing ideas and did not find a similar one
           required: true
-        - label: I added a very descriptive title to this idea.
+        - label: I added a very descriptive title
+          required: true
+        - label: I've clearly described the feature request and motivation for it
           required: true
   - type: textarea
     id: feature-request
@@ -26,3 +28,11 @@ body:
       label: Motivation
       description: |
         Please outline the motivation for the proposal. Is your feature request related to a problem? e.g., I'm always frustrated when [...]. If this is related to another GitHub issue, please link here too.
+  - type: textarea
+    id: proposal
+    validations:
+      required: false
+    attributes:
+      label: Proposal (If applicable)
+      description: |
+        If you would like to propose a solution, please describe it here.