Draft: Feat/add captcha browser

Adds a virtual browser based on neko to be able to solve the signal captcha challenges, including:

• Firefox policies.json to limit browser (kiosk mode is not an option as we need the right click
• Dockerfile (plus build job in .gitlab-ci.yml) to have the image ready-to-use without mounting any config file
• New view in wasi-listener frontend which includes some basic instructions and the embeded browser

Todos:

• Pass information on neko to wasi listener using env variables (hardcoded for now), especially user credentials for embedding
• Check for when the captcha needs to be solved
• Logic to display a link to the captcha browser if the captcha needs to be solved
• Way to paste the token and pass it on to signal-cli again