Here are the steps on how to do that:
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​1. Upload fonts to Google Drive

2. Share file publicly, check the "Share a file publicly" instructions here. 

Click on "Done" afterward.
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3. Right-click on the file to get the shareable link

4. Open a new tab and get file ID from the public URL :

[For example for url "https://drive.google.com/open?id=1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB" the file ID is "1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB"]

5. Create a file direct link by adding the file ID to the "https://drive.google.com/uc?export=view&id=" URL. 

[For example for file "1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB" the link will be "https://drive.google.com/uc?export=view&id=1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB" ]
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6. Create a file link which is accessible from all domains by adding "https://cors-anywhere.herokuapp.com/" before the file direct link - "https://drive.google.com/uc?export=view&id=.

[For example for file "1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB" it is "https://cors-anywhere.herokuapp.com/https://drive.google.com/uc?export=view&id=1OQIC3rZ1yuFboL-4QtFQeGTAxlQW6lJB"]
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After that, please check this article on how to add your font to DragDropr page.