Add beginner guidance and clearer structure to the ‘Get Started’ docs

[InvestorNBA]

The current page lists navigation links but doesn't guide a new developer on

• what to do first
• what tools they need, or
• why they should choose each section.

Please consider adding:

• A short introduction describing a recommended workflow
• A prerequisites section
• Short summaries for each link
• Grouping of content

[InvestorNBA]

I'd like to work on this