Create tags for alpha / beta releases

[peteruithoven]

Version 0.11.0-a has been released, but there was no tag added to this repo. Please add this to the appropriate tag.
(Also please add tags with the next releases)
I know it's a lot of work, but it's especially hard to do this afterwards.

[companje]

I created a tag for only the doodle3d-firmware.
I will update the Release checklist to place links to the release pages of the 3 repo's (doodle3d-client, print3d and doodle3d-firmware).