Render used sketch version

[martinheidegger]

Different versions of Sketch will create different sketch files. Those files might result in unnecessary commits and merge conflicts. It would be good to make better visible what version of sketch was used when creating the sketch file to make visible if the user uses an older version of sketch to open given design files.

[martinheidegger]

.ts files contain a version header at the moment. This works but it might be better if a single file could contain the version. Currently, the when a version is updated, the git log shows a all generated files to be changed and in this noise it is hard to filter out if a important change happened.