New Release 4.0.0

We need to make a new release, for testing purpose we should release a 3.99 beta version and when we fix all bugs we can go to the real 4.0.0 release.

We don't have nightly builds yet so we can upload the flatpak package here meantime we work in a development fractal repository to publish those kind of releases.

• Release 3.99 beta (!313 (merged))
• Fix escape bug (#402 (closed))
• Update changelog (!318 (merged) and !319 (merged))
• Update screenshot (!321 (merged))
• Wait for gnome-build-meta!158 (merged)
• Release 3.99.1 beta
• Check weird GTK bugs are gone (like #405 (closed))
• Release 4.0
• Ping TWIM