Update country flag images: Martinique (PNG and SVG files)

[thierryc]

This PR updates the Martinique flag to resolve issue #44.

•	The flag has been redrawn and optimized.
•	SVG and PNG versions are updated.
•	The flag is vertically centered and rounded, aligning with other Twemoji flags.
•	SVG overlap are optimized for deficiencies of SVG renderers.

This ensures visual consistency across the emoji set.

Related PR: twitter/twemoji#1116

Source:
Wikipedia: Flag of Martinique
Martinique article: Wikipedia

[thierryc]

Hi @jdecked,

I wanted to kindly check if you had a chance to review my pull request. Please let me know if there’s anything I can adjust or improve. I’m happy to make any changes if needed.

Thank you for your time and consideration!

Thierry