Add image to repository

[rcannood]

We need a thumbnail.svg image similar to the ones shown here: https://openproblems.netlify.app/results/

It needs to be added to the root of the repository.

Example:

• https://github.com/openproblems-bio/task_batch_integration/blob/main/thumbnail.svg
• It's also mentioned in the _viash.yaml: https://github.com/openproblems-bio/task_batch_integration/blob/main/_viash.yaml#L38-L39