Missing documentation on settings.blacklist

[seletskiy]

Can you, please, add documentation about adding sites to the blacklist? I can't find it in the README.md.

[brookhong]

https://github.com/brookhong/Surfingkeys#hotkey-to-toggle-surfingkeys

When Surfingkeys is turned off on some site by Alt-s, the status will be persisted in settings, for example,

"blacklist": {
    "https://github.com": 1
},

Alt-s once more will remove it from settings.blacklist. By the way, yj to dump all settings into clipboard.

Another way to disable Surfingkeys is to use settings.blacklistPattern, please refer to regex for disabling.

[seletskiy]

@brookhong: Great, thanks!