Add Kotlin goody for traversing a binary tree in level order

[miorel]

For inspiration, take a look at the TypeScript goody added in #189, currently located at workspaces/adventure-pack/goodies/typescript/traverseLevelOrder/index.ts.

[yulianka]

This issue already exists #193 .

[miorel]

This issue already exists #193 .

Oops, good catch. Guess we can rebrand this as Kotlin 😅

[willmadison]

I'm happy to take a look at this if no one else is already on it :)

[miorel]

That'd be amazing, @willmadison, thank you!