update changelog for v4.0.2 and v4.0.3

[taras]

Motivation

Changelog.md was missing the 4.0.3 release section and the 4.0.2 section did not include all of the notable release entries from the v4 branch history.

Approach

Added a new 4.0.3 section with the notable v4 changes that landed after 4.0.2, and backfilled the missing 4.0.2 changelog entry for spawn() delegating to scope.run().

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/effection@1194

commit: dbf4977

[codspeed-hq]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

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_{Comparing codex/update-v4-changelog (dbf4977) with v4 (4812872)}

[cowboyd]

Seems like there are a lot of formatting changes unrelated to the changelog. Is this an editor thing, or a different version of Deno thing?

[taras]

It's a new version of Deno. All of the PRs are failing. We're on 2.x - maybe we should lock it down further.