A simple cross-browser extension with Svelte as the popup controller.
Go to chrome://extensions/, and load ./public/ as an unpacked extension.
Go to about:debugging#/runtime/this-firefox, and load ./public/manifest.json as a temporary add-on.
Launch Safari, and enable Develop > Allow Unsigned Extensions.
Build the project, then run npm run gen:safari.
Open the generated ./safari/ project in Xcode and build the application. Then, run the application and enable the extension in Safari preferences.