Sync with upstream @ 20208769 - #2194

Same as title

Unicode art, grammar suggestions

See [MDN](https://developer.mozilla.org/en-US/docs/Glossary/CORS-safelisted_response_header) and [whatwg/fetch](whatwg/fetch#626).

The event type for `onerror()` is a vanilla `Event` that has no `message` property (or anything interesting about the error). Further info from this StackOverflow question: [Javascript doesn't catch error in WebSocket instantiation](https://stackoverflow.com/questions/31002592/javascript-doesnt-catch-error-in-websocket-instantiation/31003057#31003057).

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Fix minor typo

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

clarify wording about null and undefined equality in JS

Minor grammar improvement

Change contradicting statement

Fix typo

Update grammar

...ly-braces
docs: replace figure brackets with curly braces across all occurrences

Update article.md

Update article.md

Added unary plus to prompt inputs for type conversion.

The article's prose and inline examples use Prism.highlightElem, which
does not exist in the Prism.js API, while the demo code later in the same
article correctly uses Prism.highlightElement. Unify on the real API name.
Also pass only the element in forEach callbacks: forEach supplies
(element, index, array), which would collide with the
highlightElement(element, async, callback) signature if the method
reference is passed directly.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MizgRqMWEBSTYhJ9YhSd2g 

...ment
Fix Prism API name: highlightElem -> highlightElement in MutationObserver article

Convert prompt inputs to numbers with unary plus