added the license to all jar files

[bespaltovyj]

Issue #188

Comments for solutions:

1. I removed all apply because plugins are already applied in plugins sections
2. There are 2 Jar tasks in the gradle:
   • org.gradle.jvm.tasks.Jar
   • org.gradle.api.tasks.bundling.Jar is subtype of org.gradle.jvm.tasks.Jar.
     In build.gradle.kts by default using org.gradle.api.tasks.bundling.Jar, but Kotlin multiplatform register sourcesJar task with type org.gradle.jvm.tasks.Jar.

So I added import org.gradle.jvm.tasks.Jar to add a license to all jar tasks.

[oshai]

Thanks for the PR!