* Prevent `TypeToken` from capturing type variables
* Use hyphen for term "type-safe"
Not completely sure if that is grammatically correct, but it might make the
text a bit easier to understand.
* Update Troubleshooting Guide URLs in tests from 'master' to 'main'
* Rename system property
* Simplify system property check
* Adjust ProGuard default rules and shrinking tests
* Adjust comment
* Add shrinking test for class without no-args constructor; improve docs
* Improve Unsafe mention in Troubleshooting Guide
* Improve comment for `-if class *`
* Add code shrinking tools integration test
* Keep no-args constructor of classes usable with JsonAdapter
* Add library ProGuard rules for Gson
They are automatically applied for all users of Gson, see
https://developer.android.com/build/shrink-code#configuration-files
* Skip japicmp-maven-plugin for shrinker-test
* Add more tests for JsonAdapter, add tests for generic classes
* Extend default constructor test
* Add Troubleshooting Guide entry for TypeToken
