Add Sofiaplan to Open Data (#179)

README.md

@@ -1275,6 +1275,7 @@
 | [Recreation Information Database](https://ridb.recreation.gov/) | Recreational areas, federal lands, historic sites, museums, and other attractions/resources(US) | `apiKey` | Yes | Unknown |
 | [Scoop.it](http://www.scoop.it/dev) | Content Curation Service | `apiKey` | No | Unknown |
 | [Socrata](https://dev.socrata.com/) | Access to Open Data from Governments, Non-profits and NGOs around the world | `OAuth`| Yes | Yes |
+| [Sofiaplan](https://sofiaplan.bg/api/) | Access to urban research data for the Bulgarian capital Sofia | No | Yes | Yes |
 | [Teleport](https://developers.teleport.org/) | Quality of Life Data | No | Yes | Unknown |
 | [Umeå Open Data](https://opendata.umea.se/api/) | Open data of the city Umeå in northen Sweden | No | Yes | Yes |
 | [Universities List](https://github.com/Hipo/university-domains-list) | University names, countries and domains | No | Yes | Unknown |