Meta+Userland: Add jakt as an optional Lagom Tool

We can now use ENABLE_JAKT to pull jakt as a host tool and use it to
pre-process .jakt files into .cpp files for use in serenity applications

Userland/Utilities/hello-world.jakt

@@ -0,0 +1,3 @@
+function main() {
+    println("Hello, World, from jakt!");
+}