Performance issue template (#31944)

.github/ISSUE_TEMPLATE/feature_request.md

 ---
 name: Feature request
-about: Suggest a new idea for Flutter
+about: Suggest a new idea for Flutter.
 title: ''
 labels: ''
 assignees: ''

.github/ISSUE_TEMPLATE/performance.md

+---
+name: I have a performance problem with my application
+about: You are writing an application but have discovered that it is slow, you are
+  not hitting 60Hz, or you are getting jank (missed frames).
+title: ''
+labels: 'severe: performance'
+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 performance problem, then fill our the template below.
+     Please read our guide to filing a bug first: https://flutter.dev/docs/resources/bug-reports
+-->
+
+## Details
+
+<!--
+1.  Please tell us exactly how to reproduce the problem you are running into.
+
+2.  Please attach a small application (ideally just one main.dart file) that
+     reproduces the problem. You could use https://gist.github.com/ for this.
+
+3.  Run this app on a physical device using profile mode with Skia tracing
+     enabled, as follows:
+       flutter run --profile --trace-skia
+       Press ‘P’ to enable the performance overlay.
+
+4.  Record a video of the performance issue using another phone so we
+     can have an intuitive understanding of what happened. Don’t use
+     "adb screenrecord", as that affects the performance of the profile run.
+
+5.  Open Observatory and save a timeline trace of the performance issue
+     so we know which functions might be causing it. See "How to Collect
+     and Read Timeline Traces" on this blog post:
+       https://medium.com/flutter-io/profiling-flutter-applications-using-the-timeline-a1a434964af03#a499
+-->
+
+## Logs
+
+<!--
+     Run `flutter analyze` and attach any output of that command below.
+     If there are any analysis errors, try resolving them before filing this issue.
+-->
+
+```
+```
+
+<!-- Finally, paste the output of running `flutter doctor -v` here, with your device plugged in. -->
+
+```
+```