v0.3.0

• Require the minimum Kotlin version of 1.4.30
• Require the minimum Gradle version of 6.8
• Change runtime artifact id from kotlinx.benchmark.runtime to kotlinx-benchmark-runtime
• Publish runtime to Maven Central instead of Bintray #33
• Change plugin id from kotlinx.benchmark to org.jetbrains.kotlinx.benchmark
• Change plugin artifact id from kotlinx.benchmark.gradle to kotlinx-benchmark-plugin
• Publish plugin to Gradle Plugin Portal instead of Bintray