Documentation on default resource requests per deployment mode

[lieberlois]

Is your feature request related to a problem? Please describe.
I'm frustrated when configuring loki in the different deployment modes not being able to estimate the resources that will be used.

Describe the solution you'd like
I would want documentation on recommended resource requests and limits, similar to what the comment here suggests:

Describe alternatives you've considered
Extend the helm chart values with sane defaults.

Additional context
None.