Implement "files/:file_id/versions" API

[alessioarsuffi]

This MR introduces a new function shouldUpdateFigmaVersion that compares the remote Figma file version date with the locally stored date for a specific asset type (e.g., images, icons, typography, colors). If the remote version is more recent, it updates the local version and fetch the specified assets.

There is a new file called figma-versions.json. Which will have the following structure:

{
  "icons" : "2025-05-26T08:06:03Z",
  "images" : "2025-05-26T08:06:03Z",
  "colors" : "2025-05-26T08:06:03Z",
  "typography" : "2025-05-26T08:06:03Z"
}

This is due to the fact that we want to download one of the following asset type based on the latest figma file version.

Scenario:

• user has never invoked figma-export colors:
  The script will produce the following log before fetching the colors:

-------------------------------------------------------------------------------------
New version available for file: LlSdmGO32234CCTjkSYhBH... downloading updates now...
-------------------------------------------------------------------------------------

• user retries to download colors right after the above:

----------------------------------------------------------------------------
You are on the latest file version, nothing to download.
----------------------------------------------------------------------------

If the designer releases a new file version, the subsequent commands will fetch the selected assets.

✅ Changes:

• Added shouldUpdateFigmaVersion to detect and sync the latest Figma version per asset key.
• Implement files/:file_id/versions Figma API

Possible enhancements:

• Possibility to set "figma-versions.json" file via terminal command;
• Save the fileId (light and dark) to "figma-versions.json" to better track the versions ?

If you have any further comment, idea, question etc I'm open for feedbacks :)
Thank you

[alessioarsuffi]

Don't know who to tag, suggestions are more than welcome, many thanks 💪