Goreleaser

[dennis-tra]

fixes #60

goreleaser built the root directory which only contained the prefix generation code. GoReleaser should instead compile the main package in ./cmd/nebula. This PR fixes that. It also:

• extends the version/commit handling, especially how the values are passed into the binary at compile time
• add GoReleaser workflow draft (a push of a new tag should automatically publish a new draft release)

@cortze could you take over this branch? 1) fix anything you think is wrong by directly pushing on this branch 2) merge it 3) tag the commit and push that tag 4) verify that the workflow works

[cortze]

Surely!