chore: bump tsdown and @apst/tsdown (#104)

Bumps [tsdown](https://github.com/rolldown/tsdown) and [@apst/tsdown](https://github.com/alpheusday/tsdown/tree/HEAD/package). These dependencies needed to be updated together.

Updates `tsdown` from 0.19.0 to 0.20.1
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.19.0...v0.20.1)

Updates `@apst/tsdown` from 0.1.1 to 0.1.2
- [Release notes](https://github.com/alpheusday/tsdown/releases)
- [Changelog](https://github.com/alpheusday/tsdown/blob/main/package/CHANGELOG.md)
- [Commits](https://github.com/alpheusday/tsdown/commits/tsdown@0.1.2/package)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.20.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
- dependency-name: "@apst/tsdown"
  dependency-version: 0.1.2
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package.json

@@ -3,9 +3,9 @@
     "devDependencies": {
         "@apst/biome": "~0.3.0",
         "@apst/tsconfig": "~0.1.3",
-        "@apst/tsdown": "~0.1.1",
+        "@apst/tsdown": "~0.1.2",
         "@biomejs/biome": "^2.3.11",
-        "tsdown": "~0.19.0",
+        "tsdown": "~0.20.1",
         "typedoc": "~0.28.16",
         "typedoc-plugin-markdown": "^4.9.0",
         "typescript": "^5.9.3"