Add contributors

We have a [contributors.md](https://github.com/alan-turing-institute/AutisticaCitizenScience/blob/master/contributors.md) file that lists all our community members..... although maybe its better to merge this into one table in the README file as made by the [all-contributors bot](https://github.com/all-contributors/all-contributors-bot).

This issue will always stay open as a place for us to update that table :smiley_cat:

Start by comparing contributors.md with the README and review the all-contributors bot reference in the issue. Confirm whether the project wants to retain the standalone list or merge it into one README table; done means the contributor information is updated in the agreed location and the issue remains usable for future updates.

Written by the indexing model from the issue text.