Dotty/ Scala 3 support

[rmorais]

if possible, we could add support for Dotty.
I will read into what is needed but given that Vulcan already supports scala 2.13, it should be simple.
Still need to check dependencies

[bplommer]

If at some point we want to statically validate Avro schemas, I suspect we’ll have more luck if we do that in Dotty and then consider backporting it to Scala 2.

[bplommer]

I ran into scala/scala3#9492 while trying to port to scala 3.

[bplommer]

Resolved by #239