Use packages from registry instead of github

[emanuelb]

From packages.json:

    "electrum-client": "https://github.com/BlueWallet/rn-electrum-client",
    "react-native-qrcode-scanner": "https://github.com/moaazsidat/react-native-qrcode-scanner",

it use git repo instead of yarn/npm registry, which require additional git dep to compile the app & repo can be removed/relocated/changed in a way that will break the build, using packages is better.

The react-native-qrcode-scanner can be used as it's available in yarn/npm registries. https://yarnpkg.com/package/react-native-qrcode-scanner https://www.npmjs.com/package/react-native-qrcode-scanner

regarding rn-electrum-client it's not available yet, opened issue about it at: https://github.com/BlueWallet/rn-electrum-client/issues/7