Use https://github.com/Kotlin/dataframe/tree/example-projects-archives links more widely in example READMEs

[koperagen]

We have a page with link for direct download of project directories: https://github.com/Kotlin/dataframe/tree/example-projects-archives

We don't have these links in root readme for examples: https://github.com/Kotlin/dataframe/tree/master/examples

Only in some of project specific READMEs https://github.com/Kotlin/dataframe/tree/master/examples/projects/kotlin-dataframe-plugin-gradle-example and https://github.com/Kotlin/dataframe/tree/master/examples/projects/kotlin-dataframe-plugin-maven-example