feat: create GitHub prerelease and attach APK

[Batmancpu]

Update .github/workflows/build.yml to automatically create a GitHub Prerelease on successful build using softprops/action-gh-release@v2. Set contents: write permissions so the action has rights to publish the release, and attach expBoard-debug.apk to it.

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PR created automatically by Jules for task 6992261705846783620 started by @Batmancpu

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