provide shields.io compatible style customization

[scarf005]

Clear and concise description of the problem

https://shields.io provides following badge styles: flat (default), flat-square, plastic, for-the-badge, social.

currently shield.deno.dev lacks styles other than flat, soft-locking other available badge styles in order to maintain uniform style.

Suggested solution

• accept additional query parameter, style compatible with shields.io.
• provide a selector near Copy Markdown button to choose between badge styles.

Alternative

No response

Additional context

No response