Add docs/changelog for EventTarget/AbortSignal improvements

[jasnell]

workerd PR: cloudflare/workerd#7053

Summary

see workerd PR: cloudflare/workerd#7053

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[jasnell]

Change landed in workerd

[cloudflare-docs-bot]

Review

✅ No issues found in commit a2bcb00.

Code Review

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Conventions

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Style Guide Review

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[cloudflare-docs-bot]

⚠️ @jasnell This pull request adds a changelog entry dated in the past:

• src/content/changelog/workers/2026-08-19-abort-signal-global-scope.mdx — dated 2026-08-19
• src/content/changelog/workers/2026-08-19-event-spec-compliance.mdx — dated 2026-08-19
• src/content/changelog/workers/2026-08-19-spec-compliant-dispatch-exceptions.mdx — dated 2026-08-19

Typically, changelog entries should be dated the day they merge. This is not blocking — if the date is unintentional, please update it.

[cloudflare-docs-bot]

Review coverage

✅ All 2 ownership areas are covered.

✅ 2 areas already covered

Area	Approved by
Other 1 file changed /src/content/compatibility-flags/	irvinebroque
workers 3 files changed	irvinebroque

CODEOWNERS mappings for displayed areas (2)

Pattern	Owners
/src/content/compatibility-flags/	@GregBrimble, @irvinebroque, @MattieTK, @mikenomitch, @cloudflare/product-owners
/src/content/changelog/workers/	@GregBrimble, @irvinebroque, @korinne, @MattieTK, @mikenomitch, @vy-ton, @WalshyDev, @cloudflare/deploy-config, @cloudflare/dev-plat-leads, @cloudflare/workers-runtime-1, @cloudflare/wrangler, @cloudflare/pm-changelogs, @cloudflare/product-owners