govulncheck-action: allow users to use specific version of govulncheck

[sbp-bvanb]

Proposal Details

The action contains:
go install golang.org/x/vuln/cmd/govulncheck@latest

Suggestion is to add an input that points to latest, that allows users to overwrite it with a specific version.

[seankhliao]

Why would you need a specific version?

[sbp-bvanb]

To prevent that our workflow will break if breaking changes would be introduced to the latest version of govulncheck.