docs: improve base-ui README with component overview and usage examples

[crStiv]

What changed? Why?

Enhanced the base-ui library README from a minimal 2-line file to a comprehensive overview including:

• Clear description of library purpose
• Component listings (Button, Select, Icon)
• Hooks and utilities documentation
• Usage examples
• Dependencies information

Notes to reviewers

This is purely documentation - no code changes. The README now properly describes what base-ui offers and how to use it, making it easier for contributors and users to understand the library's scope.

How has it been tested?

Documentation change only - no functional testing required.

Have you tested the following pages?

BaseWeb

• Not applicable - README documentation change only
• base.org
• base.org/names
• base.org/builders
• base.org/ecosystem
• base.org/name/jesse
• base.org/manage-names
• base.org/resources

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

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