Update README.md with Android ProGuard configuration

[daveo89]

Add Android ProGuard configuration for AssemblyAI SDK

Add necessary ProGuard keep rules to README.md to ensure proper functionality of the AssemblyAI SDK when code shrinking is enabled in Android release builds.

This documentation helps developers avoid potential runtime issues when using the SDK with minification enabled.

[marcusolsson]

Thank you for you contribution! I'm not familiar with ProGuard (or Android development in general) so I'll need to read up before I can accept the PR. Could you maybe give a bit more detail to help me understand the change? Maybe link to relevant documentation?

[daveo89]

Thank you for replying.
Sure, here's the link to the official Android documentation, which should help demystify the topic. Another thing worth considering is a dedicated ProGuard configuration for the JAR library (see the 'Library dependencies' section).
Nevertheless, the majority of Android apps enable R8 functionality in the release version, and using third-party SDKs without a proper ProGuard setup might lead to runtime crashes in production without a clear explanation. That’s why a proper R8 configuration is necessary, either on the client side or within the library.

[marcusolsson]

Thank you for the links and for clarifying 🙏

[marcusolsson]

Thank you for taking the time to contribute and walk me through this! 🙏 🙏