Whenever you want to download an image from twitter.com, there's a pretty high chance it's gonna be downloaded as a .jfif file. Jfif files are basically just JPGs, but almost no service supports them. This extension automatically renames every downloaded .jfif from twitter to .jpg.
Running npm run build
compiles the typescript code files to normal javascript.
Running npm run pack
strips out the typescript files and adds a ready-to-use extension to /dist.