Dependency on Kotlin standard library
I've updated to `4.0.0` (AndroidX version `1.0.2`, gradle build tools `28.0.3`, Android Studio `3.4.2`) and updated some call sites like `sizeRes(X)` to `size(IconicsSize.res(X))`. However, that didn't compile because there is a second (unused) overload `size(() -> IconicsSize?)` that gets compiled to a function that accepts `kotlin.jvm.functions.Function0` and this class wasn't available on my class path (I have a plain Java project), so it failed to resolve the right overload.

The (right?) solution is to add a dependency on `org.jetbrains.kotlin:kotlin-stdlib`, so currently that's `implementation org.jetbrains.kotlin:kotlin-stdlib:1.3.31`.

Ideally, the Android-Iconics would tell Gradle about this dependency, so that users don't have to do anything. Alternatively, there could be a remark in the migration guide and the main setup guide (under "1. Provide the gradle dependency") that tells users that they might need this dependency.

Edit: Just found it in the GitHub release notes. Probably worth adding to the other two places as well, as those are discoverable through GitHub search. Also there it mentions a dependency on `androidx.core:core-ktx`, so for non-Kotlin projects that would be `androidx.core:core`?