Enhancement: Add Matrixbird project

I think we should add [Matrixbird](https://github.com/matrixbird) to the list of ecosystem projects. While the project is on hiatus, I believe we should include it for the sake of completeness.

Given that the project consists of both a client and an appservice, I'm not sure how we'd classify such a project.

No file or test is named. Start by locating the ecosystem-project list in the matrix.org site and review how projects with both clients and appservices are classified. Add Matrixbird with its project link, then verify the rendered list and classification.

Written by the indexing model from the issue text.