Add YAML exclude list for color token export

[phiilu]

We have background color tokens defined on Figma, but those are only used for Android and Figma designs itself. iOS uses the OS native system background colors. Therefore we would need a way to exclude certain tokens in the config. The allow list is not a good solution for us, as we want to include new tokens automatically.

This PR adds optional exclude lists for color export in figma-export.yaml:

• common.colors.exclude
• common.variablesColors.exclude

It supports exact names and wildcard patterns.

Example:

common:
  variablesColors:
    tokensFileId: <tokens-file-id>
    tokensCollectionName: "Mobile Color Types"
    lightModeName: "Light Mode"
    darkModeName: "Dark Mode"
    exclude:
      - background
      - backgroundSecondary
      - backgroundTertiary
      - background/*

Also, docs/templates were updated and tests were added for decoding the new config fields.