Add page-experience.md (#29912)

* Add page-experience.md

Add template for Pixi to file issues on Perf WG

* Update with pass/fail and components

* Update .github/ISSUE_TEMPLATE/page-experience.md

Co-authored-by: Caroline Liu <10456171+caroqliu@users.noreply.github.com>

* Update .github/ISSUE_TEMPLATE/page-experience.md

Co-authored-by: Caroline Liu <10456171+caroqliu@users.noreply.github.com>

Co-authored-by: Caroline Liu <10456171+caroqliu@users.noreply.github.com>

.github/ISSUE_TEMPLATE/page-experience.md

@@ -0,0 +1,48 @@
+---
+name: Page experience 
+about: Used to report issues where AMP pages don't meet page experience criteria.
+title: "Page experience issue"
+labels: 'Type: Page experience'
+assignees: ''
+
+---
+
+<!--
+Please only file issues when your AMP page isn't performing well on page experience and the [AMP Page Experience checker](go.amp.dev/page-experience)
+Replace/remove all of the text in brackets, including this text.
+-->
+
+Details
+---
+
+This page is failing for the following reason:
+<!--
+- Cache passes all criteria, Origin fails one or more criteria, Page experience checker had no feedback to provide.
+- Cache fails one or more criteria, Origin passes all criteria
+- Cache and Origin fail one or more criteria, Page experience checker had no feedback to provide.
+
+-->
+
+| Metric                  | Field data - Origin | Field data - Cache | Lab data - Origin | Lab data - Cache |
+|-------------------------|---------------------|--------------------|-------------------|------------------|
+| LCP                     | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| FID                     | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| CLS                     | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| HTTPS                   | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| Safe browsing           | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| Mobile-friendliness     | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+| Intrusive Interstitials | <pass/fail>         | <pass/fail>        | <pass/fail>       | <pass/fail>      |
+
+Notes
+---
+
+Components in use: 
+<!--
+List components being used on the page
+-->
+
+<!--
+<Additional notes>
+-->
+
+/cc @ampproject/wg-performance