[readme] Improve gradle-plugin readme

* Describe framework and dynamic library building
    * Describe setting custom targets for an artifact

FAQ.md

@@ -14,7 +14,7 @@ garbage.
 
 Q: How do I create shared library?
 
-A: Use `-produce dynamic` compiler switch, or `konanArtifacts { dynamic {} }` in Gradle.
+A: Use `-produce dynamic` compiler switch, or `konanArtifacts { dynamic('foo') {} }` in Gradle.
 It will produce platform-specific shared object (.so on Linux, .dylib on macOS and .dll on Windows targets) and
 C language header, allowing to use all public APIs available in your Kotlin/Native program from C code.
 See `samples/python_extension` as an example of using such shared object to provide a bridge between Python and