Improve docs with more 'applied' examples

[jfy133]

A general issue I've had with the docs is that I often am unable to understand them in the context of my specific usecase: validating samplesheets.

It would be good to improve some of the docs to include more practical examples and 'best-practice' suggestins for most common usecases.

https://nfcore.slack.com/archives/C070369GP7T/p1737461104267239

[nvnieuwk]

@jfy133 could you take a look at #141 if this is enough for you?

[jfy133]

I'm not really sure... I don't see any schema files in that PR, nor descriptions how the schema is working achieve the examples' goals