docs: adding large datasets to s3://nf-core-awsmegatests

[nickp60]

Is your feature request related to a problem? Please describe.
We are working on releasing a pipeline which will require some large databases to be hosted on s3://nf-core-awsmegatests. There is a line mentioning "Request upload to nf-core AWS S3 test buckets in the [#request-core]" but its unclear what exactly. that entails.

Describe the solution you'd like
It would be great to have the same level of detail we have for uploading datasets to nf-core/test-datasets. Perhaps this could include

• how to document the provenance of files we hope to upload
• what tools are needed to do the transfer
• whether any tests of the data need to be in place
• limitations on file sizes
• info on attribution for data
• any information about versioning of databases

Thanks!