Custom folder thumbnail text

**Describe the idea / solution you'd like**
Similar to the `.folder.png` functionality, a `.folder.txt` file would make the folder it's within use the text inside the file instead of "folder" for the thumbnail.

**Describe any alternatives you've considered**
Making a `a.[folder text]` file, downloading the generated thumbnail for it, converting that to a png, and uploading it as `.folder.png`