Default Key bindings

[alanedelman]

New users of Julia sometimes are also new users to vscode and have no clue
about things such as Cntrl+Shift+P and key bindings, and even what the below really means

great if we can have a picture of default bindings (in mac? linux? windows?)

still a new user wants to know only

• execute this line
• execute the whole file
  and has no clue what a cell is. (To be clear, a new user can probably guess that a cell
  is a group of lines, but in vscode, it's hard to tell, exactly which lines constitute a cell
  because there is no visual -- i have to look for ##
  (in jupyter, pluto, mathematica etc it is visually obvious, but not in vscode)

also a link to https://code.visualstudio.com/shortcuts/keyboard-shortcuts-macos.pdf
is mildly useful (a bit too much for a new user, and doesn't have the most important
Julia bindings above, but still useful)