slash commands

[bridiver]

picking up from #3294 there are a bunch of other potential users for slash commands.
/watch brave.com get notifications when brave.com changes
/email [email protected] create a new email message to [email protected] in email client/web email client
/remind me to download brave at 10:30 create a notification in calendar app
/prefs shortcut for about:preferences
ifttt integration
user definable shortcuts

[bridiver]

/burner email creates a new burner email and copies to the clipboard or pastes in a form - also usable from inside form fields or integrated as part of autofill

[bridiver]

slash commands should appear in the autosuggestions
in contrast to #3294 I think autosuggestions should still display search results to prevent the "impossible search query"

[bridiver]

these will be :email ... instead to avoid conflicts with file urls

[Ornataweaver]

#790 #824 #3053 #3294 #4210