Disable PNG crunching for reproducibility
This can help to prevent non-determinism introduced by the crunching process.
More information: https://gitlab.com/fdroid/fdroid-website/commit/e48f9f0773568d92ff764ad3cc79eed0ae2c497e
With enabled and disabled crunching, the size of the signed release APK was 17809681 bytes.
Related to #164 (closed)