Implement apk signer v2 or automatically downgrade Target Sdk Version to 29

[AlexisHamon]

If we don't, all apks with a tarfet Sdk version to 30+ will not be installed by adb. Something like :

adb: failed to install base.apk: Failure [INSTALL_PARSE_FAILED_NO_CERTIFICATES: Scanning Failed.: No signature found in package of version 2 or newer for package ~~~~] Error: Failed to run 'adb install base.apk'.

[AlexisHamon]

Downgrading to target sdk 29 can be easely done by editing apktool.yml after have been decoding the apk.

[annervisser]

I implemented apk signer v2 in this PR: https://github.com/NickstaDB/patch-apk/pull/32