Create a release when a tag is pushed

[stuartleeks]

The goal of this PR is to automatically create a GitHub release (example here) when a git tag is pushed to the repo:

git tag v0.1.2
git push origin v0.1.2

Changes in PR:

• Add a go.mod file
• run go mod vendor to vendor in dependencies
• Add GitHub action to respond to new tags and run goreleaser to create x86 and x64 Windows binaries for the release