Added StartPage completion

[matthewblott]

StartPage is a popular search engine which should be included.

[philc]

Hey @matthewblott,

Completions got reworked a bit, and the parse function needs to be updated to this:

parse(text) {
  return Array.from(JSON.parse(text)).map((suggestion) => suggestion.phrase);
}

More importantly, I couldn't get the suggestions API to work with the URL in this PR. It seems the website adds a random token (sc) to the query string, and that is required to get results. E.g.:

https://www.startpage.com/suggestions?q=hey&sc=mErAnqplBxxn00&lui=english

I'm not sure if that's a session token or something. It seems to me that their suggestions API isn't stable, or it isn't meant to be used programmatically like this.

[philc]

Closing due to inactivity.