Cardano Updates

- Add one-paragraph and two-paragraph style descriptions for the MRP
- Clarify roles of Core and Community Maintainers with detailed responsibilities
- Include links to relevant resources for better understanding of the program

- Revise the overview to include a direct link to the official OSC MRP page for better accessibility to detailed information on eligibility and funding.

- Clarify the title to include the full name of the program
- Update descriptions for Core and Community Maintainers to better reflect roles and responsibilities
- Improve links and references for governance and eligibility criteria

- Remove outdated link to the Maintainer Retainer page
- Emphasize the importance of linking to the official OSC page for up-to-date information

- Add MRP overview with link to official OSC page
- Add link preview card with og:image and Intersect-style layout
- Category label: MRP; sidebar title from frontmatter

Signed-off-by: thisisobate <[email protected]>