Add RescueGroups Pet API

README.md

@@ -6,6 +6,7 @@ A collective list of JSON APIs for use in web development.
 | API | Description | OAuth |Link |
 |---|---|---|---|
 | Petfinder | Adoption | No | [Go!](https://www.petfinder.com/developers/api-docs/) |
+| RescueGroups | Adoption | No | [Go!](https://userguide.rescuegroups.org/display/APIDG/API+Developers+Guide+Home) |
 
 ### Anime