Add GunPolicy.org (#2696)

README.md

@@ -896,6 +896,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Federal Register](https://www.federalregister.gov/reader-aids/developer-resources/rest-api) | The Daily Journal of the United States Government | No | Yes | Unknown |
 | [Food Standards Agency](http://ratings.food.gov.uk/open-data/en-GB) | UK food hygiene rating data API | No | No | Unknown |
 | [Gazette Data, UK](https://www.thegazette.co.uk/data) | UK official public record API | `OAuth` | Yes | Unknown |
+| [Gun Policy](https://www.gunpolicy.org/api) | International firearm injury prevention and policy | `apiKey` | Yes | Unknown |
 | [INEI](http://iinei.inei.gob.pe/microdatos/) | Peruvian Statistical Government Open Data | No | No | Unknown |
 | [Interpol Red Notices](https://interpol.api.bund.dev/) | Access and search Interpol Red Notices | No | Yes | Unknown |
 | [Istanbul (İBB) Open Data](https://data.ibb.gov.tr) | Data sets from the İstanbul Metropolitan Municipality (İBB) | No | Yes | Unknown |