Add "feature request" issue template (#30327)

.github/ISSUE_TEMPLATE/ACTIVATION.md

@@ -3,6 +3,9 @@ name: I am having difficulty installing Flutter or getting it to work
 about: You have run into problems while downloading or installing Flutter, or the
   "flutter" tool is crashing, or you are running into some other issue before even
   being able to use "flutter run".
+title: ''
+labels: ''
+assignees: ''
 
 ---
 
@@ -11,12 +14,12 @@ about: You have run into problems while downloading or installing Flutter, or th
      If you are looking for support, please check out our documentation
      or consider asking a question on Stack Overflow:
       * https://flutter.dev/
-      * https://docs.flutter.io/
+      * https://api.flutter.dev/
       * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
 
      If you have found a bug or if our documentation doesn't have an answer
      to what you're looking for, then fill our the template below. Please read
-     our guide to filing a bug first:  https://flutter.dev/bug-reports/
+     our guide to filing a bug first: https://flutter.dev/docs/resources/bug-reports
 -->
 
 ## Steps to Reproduce

.github/ISSUE_TEMPLATE/BUG.md

@@ -2,6 +2,9 @@
 name: I have a problem with my Flutter application.
 about: You are writing an application with Flutter but the application is crashing
   or throws an exception, a widget is buggy, or something looks wrong.
+title: ''
+labels: ''
+assignees: ''
 
 ---
 
@@ -10,12 +13,12 @@ about: You are writing an application with Flutter but the application is crashi
      If you are looking for support, please check out our documentation
      or consider asking a question on Stack Overflow:
       * https://flutter.dev/
-      * https://docs.flutter.io/
+      * https://api.flutter.dev/
       * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
 
      If you have found a bug or if our documentation doesn't have an answer
      to what you're looking for, then fill our the template below. Please read
-     our guide to filing a bug first:  https://flutter.dev/bug-reports/
+     our guide to filing a bug first: https://flutter.dev/docs/resources/bug-reports
 -->
 
 ## Steps to Reproduce

.github/ISSUE_TEMPLATE/SUPPORT.md

@@ -2,6 +2,9 @@
 name: I want help writing my application
 about: You have a question for how to achieve a particular effect, or you need help
   with using a particular API.
+title: ''
+labels: ''
+assignees: ''
 
 ---
 
@@ -9,7 +12,7 @@ about: You have a question for how to achieve a particular effect, or you need h
 
      Please check out our documentation first:
       * https://flutter.dev/
-      * https://docs.flutter.io/
+      * https://api.flutter.dev/
 
      If you can't find the answer there, please consider asking a question on
      the Stack Overflow Web site:

.github/ISSUE_TEMPLATE/feature_request.md

+---
+name: Feature request
+about: Suggest a new idea for Flutter
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+<!-- Thank you for using Flutter!
+
+     If you are looking for support, please check out our documentation
+     or consider asking a question on Stack Overflow:
+      * https://flutter.dev/
+      * https://api.flutter.dev/
+      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
+
+     If you have found a bug or if our documentation doesn't have an answer
+     to what you're looking for, then fill our the template below. Please read
+     our guide to filing a bug first: https://flutter.dev/docs/resources/bug-reports
+-->
+
+## Use case
+
+<!--
+     Please tell us the problem you are running into that led to you wanting
+     a new feature.
+
+     Is your feature request related to a problem? Please give a clear and
+     concise description of what the problem is.
+
+     Describe alternative solutions you've considered. Is there a package
+     on pub.dartlang.org that already solves this?
+-->
+
+## Proposal
+
+<!--
+     Briefly but precisely describe what you would like Flutter to be able to do.
+
+     Consider attaching images showing what you are imagining.
+
+     Does this have to be provided by Flutter directly, or can it be provided
+     by a package on pub.dartlang.org? If so, maybe consider implementing and
+     publishing such a package rather than filing a bug.
+-->