Documentation: Charts can be displayed as Heatmaps

[kickoke]

TL;DR: The Netdata cloud engineering team works on a new way to visualize data: Heatmaps!

See issue 265.

This initiative is driven by @hugovalente-pm and is the point of contact for further research.

Research:

• Existing documents: Collect input from engineers

Production

• Existing documents: Update collectors that support heatmaps
• Existing document: Update section to describe how to change chart types. https://learn.netdata.cloud/docs/cloud/visualize/interact-new-charts
• Existing document: API documentation on swagger should contain the option "heatmap" (Done by cloud BE team)
• Get technical review
• Get peer review
• Publicize new feature @jlbriston

Publish

• Merge PR
• Approve ingest PR on netdata/learn
• Publish social media post for heatmaps
  @jlbriston You decide where to make this feature known the best. :)