Create documentation page in the wiki

[fedorov]

For now, we will use a single-page documentation to cover most important features, and will add content to that page as needed.

We should include the following:

• configuration to use external server and how to enable the "link" icon in the UI (follow up on Configurable servers #5)
• ...

[igoroctaviano]

@pedrokohler

• Add a new section showing how to enable the tool that allows the user to change the main data source on the fly
• Add a new section showing how to use the gcp query param as a secondary data source to retrieve annotations or derived datasetets
• Add a new section showing how to customize the highlight color of annotations and how to change the color of each annotation (this would require some investigation to see how this works, you can find examples in the public folder)
• Add a new section showing how to disable all annotations (read only mode): disableAnnotationTools property and how to disable worklist (disableWorklist property)