Update `save` command

[rwols]

Nice work on these docs. It looks like the save command is outdated. When looking in my console with sublime.log_commands(True), it has an additional argument:

command: save {"async": true}

[FichteFoll]

We will redo commands entirely, as mentioned in #5, but thanks for the reminder. I'll make sure to go over various existing notes, todo marks, etc, to ensure that the rewrite will cover them.