Kotlin code execution

[edwardsnjd]

This uses Kotlin's support for scripts with the .kts extension i.e. kotlin temp.kts.

There's also experimental support in the compiler for script customization e.g. the .main.kts file extension allows for importing other files and dependencies but since this doesn't seem to be well documented this PR sticks to the conservative option.

See:

• https://kotlinlang.org/docs/command-line.html#run-scripts
• https://kotlinlang.org/docs/custom-script-deps-tutorial.html

Changes Introduced

• Language execution definition
• Code block example