Support asset paths that include % and [, etc

[CORDEA]

Hi team, thank you for the great package!
I found a small problem, and tried to fix it. Could you please check it?

Error details

In the current release, the following error occurs when characters such as % are used in the asset path.

package:flutter/src/services/asset_bundle.dart 339:7  PlatformAssetBundle.load
package:golden_toolkit/src/font_loader.dart 30:37     loadAppFonts

Unable to load asset: "packages/custom_font/fonts/Raleway-Regular%25test.ttf".
The asset does not exist or has empty data.

I found that some characters such as % and [ in the asset path included in fontType are encoded. For example, Raleway-Regular!@$%^&*()[].ttf will be Raleway-Regular!@$%25%5E&*()%5B%5D.ttf.

How to reproduce

Create a package containing custom fonts like below.

flutter:
  fonts:
    - family: Raleway
      fonts:
        - asset: fonts/Raleway-Regular%test.ttf

And the create a widget using this font.

class CustomFontLabel extends StatelessWidget {
  const CustomFontLabel({super.key, required this.text});

  final String text;

  @override
  Widget build(BuildContext context) {
    return Text(
      text,
      style: const TextStyle(
        fontFamily: 'Raleway',
        package: 'custom_font',
        fontSize: 46,
      ),
    );
  }
}

Write a golden test using this widget on the app side, and it will fail.

void main() {
  setUp(() async {
    await loadAppFonts();
  });

  testGoldens('test', (tester) async {
    const widget = WidgetUsingCustomFontLabel();
    await tester.pumpWidgetBuilder(
      widget,
      wrapper: materialAppWrapper(),
    );
    await screenMatchesGolden(tester, 'test');
  });
}