chore: setting up gradlew in multiplatform-library.md (#1541)
chore: setting up gradlew in multiplatform-library.md (#1541)

* Update multiplatform-library.md

Add instructions for setting up gradlew in a new multiplatform project.

* Add graddle wrapper instructions for new project

JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn,JetBrains/kotlin-web-site,JetBrains/kotlin-web-site,hltj/kotlin-web-site-cn