Add App Startup library

[dev-weiqi]

trafficstars

First of all thank you for this awesome project. I added App Startup library in this project and the user doesn't need to initialize manually anymore!

I also fixed the build issues. ActivityLifecycleCallbackExtTest using reflect modifiers. It's no longer supporting on JDK16 or later. (I'm not native speaker, sorry for any grammatical mistakes)

• [x] ./gradlew build -> BUILD SUCCESSFUL
• [x] ./gradlew spotlessApply -> BUILD SUCCESSFUL

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +1.00 :tada:

Comparison is base (01e3a52) 87.31% compared to head (19410b2) 88.32%.

Additional details and impacted files

@@            Coverage Diff             @@
##           v1.1.0      #20      +/-   ##
==========================================
+ Coverage   87.31%   88.32%   +1.00%     
==========================================
  Files           9       10       +1     
  Lines         134      137       +3     
  Branches       19       19              
==========================================
+ Hits          117      121       +4     
  Misses          9        9              
+ Partials        8        7       -1     

Flag	Coverage Δ
unittests	88.32% <100.00%> (+1.00%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ssionFlow/initializer/PermissionFlowInitializer.kt	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[PatilShreyas]

@dev-weiqi CodeCov is failing due to coverage impact, could you please add basic tests for the initializer?