keyboard shortcut for save

[feste]

from mike:

• remapping apple+S / cntl+S for save in playspace would be really helpful - that way you can save a lot of clicks.
  - even doing shift+apple+S for save as would be nice too, if you want this to be a good dev environment for efficient use.
  - I lost work by writing code that crashed the browser through slow inference (so considering saving before running might be good also).