Add documentation for sidecar to site

[golanha]

Documentaion will refere to adding side care by json defintion and not in UI.
Documentaion will show an example of a side car that includes: PVC, resoueces environment variables and image.
Common errors will be mentioned and an explantion on how it looks:

1. Wrong image
2. Failing on car side startup
3. insuficient resources.

Also mention the fact that there could be multiple side cars and their name must be unique