Improve onboarding by adding a clear starting point in Base documentation

## Overview
The `base/docs` site includes comprehensive documentation, but it is not always obvious where new users should begin. A clearer starting point would help readers navigate the docs more confidently.

## Problem Description
Many users land on individual pages without understanding how the documentation is structured overall. Without a guided entry point, it can be difficult to identify which topics are essential and which are more advanced.

## Expected Behavior
Users should be able to quickly find a recommended path through the documentation based on their goals. Foundational concepts and next steps should be clearly highlighted.

## Proposed Solution
Introduce a dedicated “Getting Started” page that explains the structure of the documentation and links to key foundational topics. The page should help users choose the right reading path depending on what they want to build or learn.