Add info about how to debug runs

[rcannood]

From openproblems-bio/task_batch_integration#22 by @mumichae :

Debugging nf-tower runs

The actual benchmark is run on the nf-tower platform.
You can find runs related to the batch integration by filtering for label:task_batch_integration, selecting a specific run and browsing the outputs.

For debugging purposes, you can download the output of a task run from nf-tower following command:

common/scripts/fetch_task_run \
  --input s3://openproblems-work/work/<process ID>\
  --output temp_output

You can find the process ID under the "Work directory" section of the Task details.