This quick and dirty Firefox/Chrome extension adds a "Preview" button on signal.art, that
allows to open a pack on signalstickers.com for easier preview.
Go to URL about:config, search for xpinstall.signatures.required and double-click on the value to set it to false.
Then, in about:addons, click on the wheel, select "Install add-on from file", and select signal.art_preview-[version].zip.
Go to URL chrome://extensions/, enable Developper mode, then load this folder.
A packaged version is available in the `web-ext-artifacts' directory.
Install Firefox's tool Web-ext.
Then, do web-ext build.
