Fix SD Card Image

The image.ub file for the SD card image was missing the root filesystem. This is fixed by adding cpio.gz to CONFIG_SUBSYSTEM_RFS_FORMATS.

The main changes are in commit 71594221 that were pushed accidentally into an unprotected main. This MR is to trigger the pipeline to get a firmware build.

Also added a CHANGELOG.md to keep an overview of important changes in a major/minor release.