ci: create new release notes script; use GitHub mentions

[AprilSylph]

Alternative PR title: "baby's first node script"

Description

What if every release in this repo actually had the "contributors" footer, rather than just bare author names on the listed commits?

This completely redoes the release notes script/action to use the GitHub API to achieve just that, with commit author names swapped out for mentions. Since bot accounts cannot be mentioned, they are linkified manually instead.

I feel like this could conceivably provide extra motivation for someone capable to become a contributor...?
I know it would at least feed my ego more to see my face†, not just my name, on a release's credits‡.

† ^{Well, it's not my physical face, but it's the face I choose to represent myself online, so... analogy still stands!}
‡ ^{I already get this on every release here because I'm the one doing the releases, so this isn't a factor in my wanting to do this, to be clear!}

This is primarily designed to be run via GitHub Actions, but it can still be ran locally. Without configuration, it makes unauthenticated API requests to the base repo to fetch commit details.

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Example output:

- 752a523d14e70f8d6d15502e41b6da3cc1f5a7b6 @marcustyphoon refactor: Store memoized data on dom objects (#1946)
- 6842642264f6a1c67a8244ce0500711ec96311a2 @AprilSylph feat: add `IframePreference` component (#2096)
- 42da0ea3f315facec0020568ed7b5b68fee273ae @marcustyphoon chore: Minor CSS performance optimization (#1420)
- e227b34da8bef4a53c42146aba0d4a36256e7a83 **[dependabot[bot]](https://github.com/apps/dependabot)** build: bump jquery from 3.7.1 to 4.0.0 (#2101)
- ef7a614e3bef863b699000d13aeb073f434cb2e2 @AprilSylph refactor(UI): use web components to render preferences (#2098)
- b17b2008eff44ae1e473615428e3b5db4b5c0550 @AprilSylph refactor(Tweaks): "Restore links to individual posts in the post header" (#2100)
- 36272a504ce932221817e9f36022b17965d978c6 @AprilSylph refactor(UI): use slots to render preferences (#2107)
- edd301a6b84f372973967e9dc5f5fd58d77f190c @AprilSylph Revert "fix(Themed Posts): Temporarily disable reblog trail theming with new Tumblr A/B Test" (#2108)
- 836a6648633017036ea5653f6cfbf8cb8c88104e @AprilSylph refactor(UI): render all `XKitFeature` children in `renderFeatures()` (#2111)
- 15cc897c73bf761c46218c19e80c154ecb91c352 @marcustyphoon fix(Panorama): Unexpanded media mode bugs (#2110)
- dda530baeb2b839e539b14b08e80bb94dc0149cd @AprilSylph fix(UI): unbreak feature toggling
- f89f177cacef7ca4332c24cc5afabd38647392d3 @marcustyphoon chore: Moderate CSS performance optimizations (#1644)

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Example rendered output:

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Testing steps

Look at https://github.com/AprilSylph/XKit-Rewritten/actions/runs/22062698062.

In all seriousness, I expect this to be heavier on code review than my other PRs, since I barely know what I'm doing here.

[marcustyphoon]

Two slightly interesting notes from testing a #1843 merge:

• console.warn writes to stderr, so dev/release-notes.js >> $GITHUB_STEP_SUMMARY will not include the "Could not find commit info" message.
• Set.prototype.intersection() uses the order of the smaller set; this means that in the case where we create more than 100 commits between releases, the commits will be listed in reverse-chronological order.