Drone

[plugins/github-release] Select a release as "pre-release" automatically

I have idea for ‚Äúplugins/github-release‚ÄĚ, I think we should select release as ‚Äúpre-release‚ÄĚ based on semver.org. For example when a project has these tags: v0.5.0-rc2 or v1.2.0-beta it‚Äôs better select release as a ‚Äúpre-release‚ÄĚ automaticlly.