Typos/grammar issues in settings.html

[DavidMetcalfe]

Under "Extra Header" settings, you have the following:

"You may define an extra http header to be sent with background requests
This may be useful if you sending background requests to your own server
and want the "let the server know" that these are special type of requets
Ignore this option if you not using this extension to communicate with your own server"

What it should probably read is like so:

"You may define an extra HTTP header to be sent with background requests.
This may be useful if you sending background requests to your own server
and want to "let the server know" that these are a special type of request.
Ignore this option if you not using this extension to communicate with your own server."