Coliding articles about feature preview

[tomasMizera]

We have two places that talk about how to setup the preview panel, those are:

• https://merginmaps.com/docs/tutorials/further-project-customisation/#customising-the-preview-panel <- in tutorials
• https://merginmaps.com/docs/gis/features/#settings-for-mergin-maps-mobile-app-preview-panel

The one in tutorials has less information and does not link to the second one that contains more details. My suggestion would be to shrink the first one and let it link to the second one, what do you think?