How to find third-party photo extensions I want to find if there is any iphoto extension can share photos on google photos.

Therefore I check
https://support.apple.com/en-gb/HT205245

it says


  Use the Mac App Store to find and install third-party extensions for Photos.


But I have no idea how to search App Store to find extension for photos.
Any idea?
As of now there only a few extensions for Mac OS X Photos. Many more will be rolling out in the near future. So the extensions available right now are:


BeFunky Express
Intensify
Tonality
Noiseless
Snapheal
Affinity Photo
Pixelmator
DxO Optics Pro
External Editors for Photos
Picktorial
Polarr
HayPhotos
Lochkamera