Comment 0 for bug 1887383

[Impact]

 * Several parts of the build, including the yaru README and github actions to stay synced with upstream, are out of date and need updates.
Those changes are:
- fix Yaru project name + update README pictures
- build: deduplicate meson.build and introduce Flavours https://github.com/ubuntu/yaru/pull/1884
- add libgtk-3-dev to the bootstrap script https://github.com/ubuntu/yaru/pull/2222
- updates to the upstream directories, which include the source code of the unmodified upstream gnome-shell and gtk3 themes https://github.com/ubuntu/yaru/pull/2084
- Use MESON_INSTALL_DESTDIR_PREFIX in post_install.py to avoid errors while building https://github.com/ubuntu/yaru/pull/2206
- Check for updates to GitHub Actions every weekday https://github.com/ubuntu/yaru/pull/2223

 * Backporting these updates to focal, will greatly improve the build process of the yaru project and help to avoid bugs and help the development of the team

 * all fixes are in yaru master since several weeks and have been tested several times

[Test Case]

 * Look at the yaru project page while in this branch https://github.com/ubuntu/yaru/tree/ubuntu/focal and find the images to be removed
* Look at the yaru project page while in the master branch https://github.com/ubuntu/yaru/tree/master and find all images to show what currently is in focal
* All other test cases are described in the corresponding pull requests

[Regression Potential]

 * Outdated versions of meson may clash with the current yaru build, otherwise, no regression potential

[Other Info]

 * Those changes are not "visible" for the end-user while using the ubuntu desktop, i.e. no theme changes, no icon changes here, but they greatly improve the daily work of the yaru team