Updated finder documentation to reflect gantry/gantry5#2561

[thexmanxyz]

Hey, I now updated the documentation of 05.advanced / 10.content-in-particles to reflect the changes made with PR gantry/gantry5#2561.

I briefly described the usage of the new finder method tags(...) as well as the parameters. I also added a note which describes how the matchAll parameter works. Because it might be confusing as it tackles ids and titles separately but not collectively. This is the intended behaviour as typically an API user would specify tags as ids or titles but not mixed - even if it works with the outlined limitation.