[Feature Request]: Thumbnail preview for `clip` files

[TrigamDev]

Checklist

• [x] I am using an up-to-date version.
• [x] I have read the documentation.
• [x] I have searched existing issues.

Description

There are currently no thumbnail previews for clip files (the project file format for Clip Studio Paint).

Solution

Add a thumbnail renderer for clip files.

Alternatives

No, clip files currently have the default, blank thumbnail.