[13.x] Add PNG, GIF, AVIF, and BMP output formats to the Image component

[Tresor-Kasenda]

Summary

Illuminate\Image\Image::toFormat() currently only supports converting to webp, jpg, and jpeg, even though the underlying Intervention Image encoders for png, gif, avif, and bmp are already bundled and used elsewhere in the driver (MediaTypeEncoder fallback). This adds first-class fluent methods for the missing formats, following the exact same pattern as the existing ones.

• Image::toPng()
• Image::toGif()
• Image::toAvif()
• Image::toBmp()

use Illuminate\Support\Facades\Image;

// Before: only webp/jpg/jpeg were reachable through toFormat()
Image::fromUpload($request->file('avatar'))
    ->cover(400, 400)
    ->toWebp()
    ->store('avatars');

// Now also possible:
Image::fromUpload($request->file('avatar'))
    ->cover(400, 400)
    ->toAvif()
    ->quality(80)
    ->store('avatars'); // stored with the correct .avif extension

Image::fromPath(storage_path('app/logo.png'))
    ->toGif()
    ->toBase64();

Image::fromUpload($request->file('scan'))
    ->toBmp()
    ->toDataUri();

Also fixes Image::extension(), which was missing the image/avif MIME type mapping and would have produced a .bin extension for AVIF outputs stored via store()/storeAs().

[taylorotwell]

Tests are failing.