Update project description and default branch
Right now the description of the project has the following:
Port of FFmpeg to the Meson build system
Workflow: merge to meson-4.4 branch, then cherry-pick into meson-4.X.Y branches which track specific releases and will stay fast-forward. Use merge commits on meson-4.4 for new upstream versions.
Is that still valid ?
The default branch is still meson-4.4
whereas it should be set to the more recent meson-6.0
branch