Bug fixes and improvements

[bretthayes]

Changelog

• Restores generateChangelogItems.go for generating changelog items for release posts. This closes #5709. Also updated the handbook to reflect this in sourcegraph/handbook#4787
• Fixes a discrepancy with our Background component where multiple utility classes would be applied based on multiple conditions being true. This caused a utility class conflict noticed on the old CaseStudyLayout for the CtaSection. Now they are scoped to their respective conditions in preparation for moving towards more code-based gradients and utility classes for backgrounds. This will help with refactoring when we remove our bg images.
• Removed another duplicate cta section (RequestDemoForm) in lieu of our new CtaSection
• Added a scrollToAnchor hook which closes #5637
• Updated caniuse-lite from a lint warning suggestion

Test

1. Ensure prettier has standardized the proposed changes.
2. Ensure anchor links smooth scroll to the top of their element (example: /terms/security#managed-sourcegraph-instances)
3. Ensure CtaSection on old case study layouts have white text on a black background (example: /case-studies/cloudflare-accelerates-debugging-and-improves-security)

[sourcegraph-bot]

Notifying subscribers in CODENOTIFY files for diff 4cbb921e6ae24de1218ac4a9af9e52fd336d7377...ccbe4dd57a9409b86772adb1c8b280f8b26d4ca8.

Notify	File(s)
@content-platform-team	scripts/generateChangelogItems.go src/components/Background/index.tsx src/components/CaseStudies/CaseStudyLayout.tsx src/components/CtaSection.tsx src/components/RequestDemoForm.tsx src/components/index.ts src/hooks/index.ts src/hooks/scrollToAnchor.ts src/pages/_app.tsx yarn.lock