Switch to proper semver Go tag name (prefixed with a "v")

[leonklingele]

Go requires Git tags to start with a v in order for them to appear as a non-pseudo-version number inside
go.mod. See https://go.dev/doc/modules/version-numbers

For example, my go.mod says

	github.com/phayes/freeport v0.0.0-20220201140144-74d24b5ae9f5

whereas this is the preferred way (and even compatible with dependabot and other tools!):

	github.com/phayes/freeport v1.0.2

Instead of tagging 1.0.2, prefix tags with v: v1.0.2.

Thank you! 😊