Update Atlas Builder to support animations based on tags

[MarcinKuder]

Aseprite allows to mark frames with tags. This allows to have a single file with multiple separate animations - e.g. see Aseprite docs for more details

This change generates a separate Animation_Name in atlas.odin for each tag found in ase file (with appropriate frame numbers). E.g.

[karl-zylinski]

Thank you! Neat!