Implement SpaceResolver.

[tilucasoli]

Description:

Currently, the framework lacks a token resolver for SpaceToken, which could manage spacing values like margins, paddings, and gaps. This task involves implementing a SpaceResolver .

User Story:

As a developer using the framework,
I want to resolve and apply standardized space tokens,
so that I can create dynamically resolve the token values.

Acceptance Criteria:

• Design and implement a SpaceResolver to handle spacing tokens based on BuildContext.
• Ensure the resolver is following the same structure of others TokenResolver.
• Write tests to validate the SpaceResolver functionality.
• Update documentation to include instructions for using the SpaceResolver.

API Reference

MixThemeData(
  spaces: {
    spaceToken: SpaceResolver((context) {
      if (MediaQuery.of(context).size.width > 600) {
        return 16.0;
      }
      return 8.0;
    }),
  },
);

[tilucasoli]

The issue we are facing is that all Resolvers were developed by extending the Token type. For example, the ColorResolver is an extension of the Color type, allowing it to be used as a color and resolved when needed. However, for Space, which is represented by a double, we encounter a problem. Since double is a final class, it CANNOT be extended.