Implementations for Ktor, Spring, and Play

[GirlInPurple]

Here is a (work-in-progress) implementation for the JVM-based HTTP server frameworks Ktor, Spring, and Play.
I am open to suggestions for more JVM-based frameworks; I ended up dropping Netty support due to time constraints.

Stuff that still needs to be done:

• General documentation improvements
  • Within the README in the /jvm/ directory
  • Within all the exposed APIs (mostly in :common)
  • Within the repo's main README
  • I am strongly considering making another PR purely for updating and adding documentation across all implementations.
• CI Tests for all 3 subprojects
  • Ktor
  • Spring
  • Play
• Backend support for all three platforms (to be specific, here)
  • I kept having to spoof being an Express server while testing an eariler version, it might be best to add an "Unknown" category for situations like this.
• Upload all 3 subprojects to Maven Central or some equivalent
  • I've had some issues with Jitpack in the past, especially for Kotlin-based multiproject repos, but if you can get it to work properly it's worth a shot.

[vercel]

@GirlInPurple is attempting to deploy a commit to the tomdraper's projects Team on Vercel.

A member of the Team first needs to authorize it.

[tom-draper]

Wow! This is fantastic. I'll do some testing as soon as I can. Great work