Review examples

[cmongut]

Current status: http://cartoframes-generate-guides-as-md.developers.carto-staging.com/developers/cartoframes/examples

• Add introduction page for each example section
• Move visualization examples to the same section Add visualization section in the developer center examples #1475
• Add description for each section
• Add an image for each section --> Next
• Add example about how to discover datasets in the developer center
• In the Load data from CARTO Table example, add tip about visualizing it directly.
• In the Load data from CARTO SQL Query example, add tip about visualizing it directly.

Finally:

• Rerun all the examples with the last version