Set up theme components

[Avishek Khan]

Why

Configure the theme to apply it throughout the app.

Acceptance Criteria

Set the following app-wide components.

• Fonts
• Colors
• Text styles

Design

N/A

Resources

• https://docs.flutter.dev/cookbook/design/themes
• https://www.figma.com/file/GjRPOjDyZ6f4EDL3wKarRK/Challenge---Mobile-App
• https://github.com/luongvo/flutter-survey/blob/develop/lib/resources/app_theme.dart