Update Documentation Storage Backends

[pocki]

Can you please update the documentations about the storage backends?
It seems that there are now lot of different backends supported (#638) but I can't find any documentation how to configure and use it.

[yurishkuro]

Configuration of officially supported backends is documented already: https://www.jaegertracing.io/docs/1.43/deployment/#span-storage-backends. For unofficial backends you have to look into their own documentation / repositories.

[pocki]

Thanks for the update. I thought, there are more official backends now. Some of them have still poor to no documentation