Handle unauthorized ADB & app installation fail, improve readme

[IGPenguin]

🤔 Check before merge:

• [x] 🏗 All functions implemented thoroughly
• [x] 🔨 All changes tested
  • [x] unauthorized ADB device, android device picker
  • [x] zero
  • [x] one
  • [x] two
  • [x] all authorized
  • [x] one authorized
  • [x] iinstall failed
  • [x] iinstall success
  • [x] ainstall failed
  • [x] ainstall success
  • [x] ainstall -a
  • [x] ascreenshot -a
• [x] 📝 Changes in usage / new scripts added to README.md
• [x] 📣 Major changes listed in changelog.txt

✅ All good? -> Merge! 🎉🎉🎉