[.github] Encourage reporters to share their ideas on the forums in feature request issue template

Author: AnthonyLatsis

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,6 +1,6 @@
 ---
 name: Feature request
-about: Suggest an idea for this project
+about: Share an idea
 title: ''
 labels: feature request
 assignees: ''
@@ -14,6 +14,17 @@ for Swift (e.g. code completion). If your feature request relates to the
 implementation of a proprietary (closed-source) Apple framework such as UIKit,
 SwiftUI, Combine, etc., please report it to https://feedbackassistant.apple.com
 instead.
+
+If you haven't found or started a thread on the Swift forums yet, consider
+socializing your idea in the "Discussion" subcategory
+(https://forums.swift.org/c/evolution/discuss) after submitting this request.
+This is an essential step toward the official review of any proposal concerning
+language or library design, and while GitHub issues do great for tracking
+purposes, the forums are far better ground for drawing attention to ideas and
+gauging interest from the community.
+
+For more information on how ideas are proposed, discussed, and reviewed, see
+https://swift.org/swift-evolution
 -->
 
 **Motivation**
@@ -31,5 +42,8 @@ Describe any alternative approaches or features that you have considered in
 addressing the problem, and why you chose this approach instead.
 -->
 
-<!-- Add any other context about your feature as appropriate. -->
+<!--
+Add any other context about your feature as appropriate. For example, link out
+to a discussion on the Swift forums (https://forums.swift.org).
+-->
 <!-- **Additional context** -->