Update cog to 0.4

[paulfantom]

There is a newer cog version which solves problems with HiDPI screens and potentially brings some more bugfixes. Could you consider updating this project dependency and release the new container image?

[marhoy]

You could try my pull request that updates to cog-0.4 and wpewebkit-2.26.
Pre-built docker-image can be found here:
https://hub.docker.com/repository/docker/marhoy/balena-wpe