Function resolveUrl

resolveUrl(base: string | undefined, relative: string): string
Resolves a relative URI against a base URI.

If the URI is absolute (has a scheme), it is returned as-is. If no base URI is provided, the URI is returned as-is. Supports http://, https://, and other standard schemes.
Parameters
- base: string | undefined
  The base URI for resolution, or undefined
- relative: string
  The relative URI to resolve
Returns string
The resolved absolute URI, or the original if already absolute
Example
```
resolveUrl('https://example.com/dir/playlist.m3u8', 'segment.ts');
// 'https://example.com/dir/segment.ts'

resolveUrl(undefined, 'segment.ts');
// 'segment.ts' (no base, returned as-is)
```
- Defined in src/utils.ts:219