Adding performance mark to PageSkeleton unmount for load tracking.

[craigbrunner]

WHY are these changes introduced?

This allows us to measure how long it takes from start of pageload to page skeleton removal without refactoring a large amount of code.

WHAT is this pull request doing?

Adds a performance mark when the page skeleton is unmounted. There is no accessibility impact or extra documentation on this, so I didn't tophat those.

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

🎩 checklist

• Tested a snapshot
• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility
• Updated the component's README.md with documentation changes
• Tophatted documentation changes in the style guide

[github-actions]

🫰✨ Thanks @alex-page! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

yarn add @shopify/polaris-icons@0.0.0-snapshot-release-20240124001003

yarn add @shopify/polaris-migrator@0.0.0-snapshot-release-20240124001003

yarn add @shopify/polaris@0.0.0-snapshot-release-20240124001003

yarn add @shopify/polaris-tokens@0.0.0-snapshot-release-20240124001003

yarn add @shopify/stylelint-polaris@0.0.0-snapshot-release-20240124001003

[craigbrunner]

/snapit

[github-actions]

🫰✨ Thanks @craigbrunner! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

yarn add @shopify/polaris-icons@0.0.0-snapshot-release-20240124210446

yarn add @shopify/polaris-migrator@0.0.0-snapshot-release-20240124210446

yarn add @shopify/polaris@0.0.0-snapshot-release-20240124210446

yarn add @shopify/polaris-tokens@0.0.0-snapshot-release-20240124210446

yarn add @shopify/stylelint-polaris@0.0.0-snapshot-release-20240124210446

[translation-platform]

Localization quality issues found

The following issues may affect the quality of localized translations if they are not addressed:

• The value Clear for key Polaris.ActionList.SearchField.clearButtonLabel is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.
• The value Search for key Polaris.ActionList.SearchField.search is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.
• The value Search actions for key Polaris.ActionList.SearchField.placeholder is very short. Short strings are more likely to be misunderstood by translators without context. Please provide additional context for the translators if possible.

Please look out for other instances of this issue in your PR and fix them as well if possible.

Questions about these messages? Hop in the #help-localization Slack channel.

[craigbrunner]

We have added this to Dev UI by wrapping loader timings.