docs: update examples.md to match current examples directory structure

[AbdulSamad94]

This PR updates the docs/examples.md file to accurately reflect the current structure of the examples/
directory. The documentation was missing several example categories and outdated in its descriptions of the
available examples.

Changes

• Updated the examples documentation to include all current example directories
• Added descriptions for previously missing categories:
  • financial_research_agent
  • memory
  • hosted_mcp
  • reasoning_content
  • And other newly added or previously undocumented examples
• Enhanced descriptions for existing categories with more detailed information about their contents
• Maintained the existing format and style of the documentation

The examples documentation was incomplete and didn't accurately represent all the available examples in the
repository. This update ensures that users can find all the examples and understand what each category
contains.

[AbdulSamad94]

@seratch done