Add 6 new FAQ questions to FAQ page

[popovayoana]

Tracking issue for the FAQ additions from #1502.

Adds 6 new Q&As across four categories:

• Integrations & API: Does PortalJS Cloud have APIs? / What are the trade-offs of moving from CKAN to PortalJS Cloud?
• Features & Functionality: Does PortalJS Cloud support geospatial visualizations? / Can PortalJS Cloud users access private datasets in the frontend?
• Technical & Hosting: Can we make changes to the portal frontend code independently?
• Support & Maintenance: Does PortalJS Cloud have documentation?

Relates to #1502