Extending Vert.x for Kotlin

Kotlin’s extensions are developed in thisdirectory.

For instancevertx-core extensions are in theio.vertx.kotlin.core package, etc…​

Extensions needs to be tested anddocumented.

Bumping Kotlin version

There are a couple of rules to follow before increasing the project versions:

• If changing one betweenkotlin andkotlinx.coroutines version, make sure that all transitive dependencies, likekotlin-stdlib, still match between the two versions.

Kotlin evolves fast, so just change the project versions, test it, and shot a PR.