Add RuneScape Wiki and OldSchool RuneScape Wiki

[Ivy-Panda]

Search strings copied from https://runescape.wiki/w/RuneScape:Finding_the_wikis_with_ease

[philc]

Thanks @Ivy-Panda for the submission!

I think this is too niche to live in the main repo -- I don't use the Runescape wiki and don't want to maintain the parsing code).

I haven't figured out a way to make search engine completions easily extensible with user-code for more niche search engines.

[rileywilddog]

JSON.parse(xhr.responseText)[1] doesn't seem like a particularly onerous maintenance burden, and this seems like the search suggestion response format basically everything (including google) supports now...

Edit: Ah, you're even aware of this... 🙃