Add helps&tooltips for most common queries in Grafana

[hagen1778]

It would be great, if plugin had some help info or tips about building basic queries:

1. How to print the recent logs
2. How to format logs output
3. How to plot time series panel
4. How to plot piechart or histogram

The point of this enhancement is to make it easier for new users to start.
It would be also great to have a reference public well-designed dashboard where everyone can play with it.

[hagen1778]

A public dashboard where we test the plugin https://play-grafana.victoriametrics.com/d/be5zidev72m80f/k8s-logs-demo?orgId=1&from=now-24h&to=now&timezone=browser&var-ds=P566C6523BE02F42C&var-namespace=&var-pod=&var-container=$__all&var-filter=%2A&var-limit=500