Add a command that prints version

[leotsarev]

Steps to reproduce:
Try to understand what version dotnet-releaser uses, so I can tag docker image manually

Expected result:
dotnet releaser should have command to output version, like

>dotnet releaser version ./my-releaser.toml
0.0.1

or any other way to determine version

[xoofx]

Ooops, I thought I had added it.