It’s true! You can upload fonts to your project on typst.app, in the root or a sub-folder and they they can be used as if you’re compiling locally and have the fonts installed. I didn’t know about this and it’s only documented on stackoverflow, so I thought I’d highlight it here.
Example Project with Raleway.
https://typst.app/project/rTQ4SnDsA16OmT9oQ96uX9
Of course, it’s up to you to obtain and adhere to any associated license for the fonts you use.