dev releases: update release date on each build

When there is a commit to master, a new dev release is built: https://github.com/bugy/script-server/releases/tag/dev
However the date of release remains the same, as when the first release was created (at the moment "bugy released this on Dec 27, 2018")

This should be fixed and the date should be updated on each release

#173 added dev tag recreation, to reset dev release date