docs: Add Arrow Protocol to projects.md (#1008)

docs/src/getting-started/projects.md

@@ -21,4 +21,5 @@ Open a pull request to add your project to the [list](https://github.com/project
 * [Quarry](https://quarry.so/)
 * [PsyOptions](https://psyoptions.io/)
 * [sosol](https://sosol.app/)
+* [Arrow Protocol](https://arrowprotocol.com/)