Upload project functionality

[jdreyesp]

It would be great if the same we can download projects we can upload projects as well. It allows interviewers to prepare stuff locally, and have them ready to be shared with the interviewed.

It should enforce the same structure so that it works fine with scastie, like having main.scala as the only source file and so on.

Cheers

[OlegYch]

this can be done using current REST api eg https://github.com/scalacenter/scastie/blob/4900371dfec3a56286b0800666c037572b1d87b0/client/src/main/scala/com.olegych.scastie.client/RestApiClient.scala#L69 though it is not well defined, it is pretty stable