Provide basic documentation about setup

[yarikoptic]

• describe in README.md how to "replicate" the setup: configuration (backups2datalad.cfg.yaml)
• describe cron jobs to setup, and why such separation

needed for @kabilar and Aaron to replicate

edit: current cron jobs I see (some are disabled temporarily... drives are migrating etc)

2 * * * * chronic flock -E 0 -e -n /home/dandi/.run/backup2datalad-cron.lock bash -c '/mnt/backup/dandi/dandisets/tools/backups2datalad-update-cron'
50 1 * * * chronic flock -E 0 -e -n /home/dandi/.run/backup2datalad-cron.lock bash -c '/mnt/backup/dandi/dandisets/tools/backups2datalad-update-cron --mode verify'
### 30 1 * * * chronic flock -E 0 -e -n /home/dandi/.run/backup2datalad-cron.lock bash -c '/mnt/backup/dandi/dandisets/tools/backups2datalad-update-cron-zarrs'
# TEMP  52 * * * * chronic flock -E 0 -e -n /home/dandi/.run/backup2datalad-populate-cron.lock bash -c '/mnt/backup/dandi/dandisets/tools/backups2datalad-populate-assets-cron'
#52 * * * * chronic flock -E 0 -e -n /home/dandi/.run/backup2datalad-populate-zarr-cron.lock bash -c '/mnt/backup/dandi/dandisets/tools/backups2datalad-populate-zarrs-cron'

[jwodder]

@yarikoptic What exactly do you want me to say about the cron jobs? How much should this part of the documentation be tied to our current setup?

[yarikoptic]

At least that that we have two types - one to populate repos, and another to do the transfer. Might be worth disclosing that we also separate ones with zarrs out since they take too long etc.

Current setup provides an example, so we could share details, but generally doesn't need to be "too tied"

[jwodder]

@yarikoptic

At least that that we have two types - one to populate repos, and another to do the transfer.

Wouldn't that be obvious from the fact that those are two different commands? I'm finding it difficult to say anything meaningful about how to set up cronjobs.

[jwodder]

@yarikoptic I've created #376 with what I've written on everything except cronjobs.