[Doc] Add Soul data provider

docs/DataProviderList.md

@@ -67,6 +67,7 @@ If you can't find a Data Provider for your backend below, no worries! [Writing a
 * ![sails Logo](./img/backend-logos/sails.svg "sails Logo")**[Sails.js](https://sailsjs.com/)**: [mpampin/ra-data-json-sails](https://github.com/mpampin/ra-data-json-sails)
 * ![sqlite Logo](./img/backend-logos/sqlite.png "sqlite Logo")**[SQLite](https://www.sqlite.org/index.html)**: [marmelab/ra-sqlite-dataprovider](https://github.com/marmelab/ra-sqlite-dataprovider)
 * ![marmelab Logo](./img/backend-logos/marmelab.png "marmelab Logo")**[REST](https://en.wikipedia.org/wiki/Representational_state_transfer)**: [marmelab/ra-data-simple-rest](https://github.com/marmelab/react-admin/tree/master/packages/ra-data-simple-rest)
+* ![soul logo](./img/backend-logos/soul.png "Soul Logo")**[Soul](https://thevahidal.github.io/soul/)**: [DeepBlueCLtd/RA-Soul](https://github.com/DeepBlueCLtd/RA-Soul)
 * ![spring Logo](./img/backend-logos/spring.svg "spring Logo")**[Spring Boot](https://spring.io/projects/spring-boot)**: [vishpat/ra-data-springboot-rest](https://github.com/vishpat/ra-data-springboot-rest)
 * ![strapi Logo](./img/backend-logos/strapi.png "strapi Logo")**[Strapi v3/v4](https://strapi.io/)**: [nazirov91/ra-strapi-rest](https://github.com/nazirov91/ra-strapi-rest)
 * ![strapi Logo](./img/backend-logos/strapi.png "strapi Logo")**[Strapi v4](https://strapi.io/)**: [garridorafa/ra-strapi-v4-rest](https://github.com/garridorafa/ra-strapi-v4-rest)