Added phys.org translator

[LaurenceOfAustralia]

Added a translator for the site phys.org, for which we previously weren't getting all metadata from. Also added support for the sites search feature. This should fix issue #2897.

This is my first time working with this codebase so i'd be grateful if whoever approves this could take a look over my code to make sure I haven't done something stupid through inexperience!

[LaurenceOfAustralia]

Thanks @AbeJellinek for helping to fix up all the mistakes I made!

I think i've fixed all the issues you raised (except for one i've asked for your advice on).

I'd also however be gratefully if you could take a look at the async code i've added. It was created mainly through cannibalising other translators because i've never used async in javascript before, so its very possible some errors have crept in.

[AbeJellinek]

Strip the tags, but otherwise, looks good!

[LaurenceOfAustralia]

Done. Thanks @AbeJellinek!