Update documentation on I/O

[m-fila]

BEGINRELEASENOTES

• Added documentation for reading and writing EDM4hep files with the IOSvc
• Moved documentation on k4DataSvc to legacy page

ENDRELEASENOTES

Some extensions (namely sphinx-design and from myst_parser colon_fence) are used to render the pages more nicely in sphinx-based documentation with admonitions and tabs (setting properties either in steering file or from command line):

Closes #212

[tmadlener]

I don't know if we need / want to mention this explicitly in the documentation but I think "IOSvc" is pretty much required as name for the IOSvc, right? At least some of the CLI examples below will only work with that. Can we create an empty IOSvc() and rely on a default name?

[m-fila]

There is a mention:

The service should be imported from k4FWCore and named "IOSvc" as other components may look for it under this name.

Yes, naming it differently might be a problem. Relaying on the default name works fine.
Added a comment

[jmcarcell]

I checked to make sure and I didn't see any errors when using a different name or no name at all for IOSvc. Only the Reader and Writer retrieve it through a ServiceHandle.

[jmcarcell]

I don't have any more comments. Anything else @m-fila?

[m-fila]

I noticed that outputCommands is not capitalized as the rest of the IOSvc properties.
I'm not sure if you want to give it similar treatment as with Input and Output properties

Otherwise that's all. Thank you very much for the comments 😄

[jmcarcell]

I had the same thought when I was reading the diffs. I'm not sure, in this case this was literally the same command as it is used with PodioDataSvc. At least with Output it was a different parameter name. So I don't have a strong opinion on changing it or keeping it as it is.