theme: add Seal Mint

[Kess-UwU]

No description provided.

[Neikon]

Thanks for the contribution.

The failing check is caused by a JSON syntax error in themes.json, not by the theme content itself.

Right now the new entry was added without a comma after the previous object. The file currently ends like this:

  }
  {
    "title": "Seal mint",

It should be:

  },
  {
    "title": "Seal mint",

After fixing that comma, the current npm test check should get past the JSON parsing step.
One additional recommendation: the image field currently uses a GitHub blob URL:

https://github.com/Kess-UwU/Seal-Mint/blob/1db0c345529d9f44fd4f6d543b5e396ed89a078e/preview(1).png
That may not render reliably as a direct image in the site. A direct raw image URL or a localized project asset would be more robust.

Thanks again for the submission.