[CLOV-807][maintenance] integrate sonarqube for backpack

[Flora Cheng (floracheng292)]

Remember to include the following changes:

• Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [Clover-123][BpkButton] Updating the colour
• README.md (If you have created a new component)
• Component README.md
• Tests
• Accessibility tests
  • The following checks were performed:
    • Ability to navigate using a keyboard only
    • Zoom functionality (Deque University explanation):
      • The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • Ability to navigate using a screen reader only
• Storybook examples created/updated
• For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here

[Copilot]

Pull request overview

This PR integrates SonarQube analysis into the Backpack repository for code quality monitoring and static analysis. The integration adds automated code scanning to the CI/CD pipeline with coverage reporting and PR feedback.

Key changes:

• Adds SonarQube configuration file with project settings and analysis rules
• Enables comprehensive Jest coverage reporting (text, clover, json, lcov formats)
• Implements SonarQube workflow job in GitHub Actions with coverage upload and PR feedback

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
sonar-project.properties	Defines SonarQube project configuration including source paths, exclusions, and coverage settings
package.json	Extends Jest coverage reporters to generate reports compatible with SonarQube
.github/workflows/_build.yml	Adds coverage artifact upload and new SonarQube job for automated code analysis

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[Copilot]

Trailing comma on line 37 in sonar.coverage.exclusions property may cause parsing issues in some SonarQube versions. Remove the trailing comma after the last pattern.

Suggested change

	**/*accessibility-test.*,\
	**/*accessibility-test.*

[skyscanner-backpack-bot]

Visit https://backpack.github.io/storybook-prs/4082 to see this build running in a browser.

[skyscanner-backpack-bot]

Visit https://backpack.github.io/storybook-prs/4082 to see this build running in a browser.

[skyscanner-backpack-bot]

Visit https://backpack.github.io/storybook-prs/4082 to see this build running in a browser.

[Flora Cheng (floracheng292)]

Add more format here, so that sonarqube can use

[Flora Cheng (floracheng292)]

This file needs to be refined after sonarqube analysis

[Flora Cheng (floracheng292)]

Sonarqube job needs read permissions