New main branch for pysteps-v2

[ladc]

Dear pysteps contributors and users,

We are working on pysteps v2.0.0. This new version will introduce breaking changes w.r.t. v1.x including:

• use of a new data model based on xarray throughout the codebase
• move to uv for python package management and better dependency version management
• replace black with ruff
  We will also more clearly define contributor and maintainer roles.

To prepare for the new version, the following changes have already been made in the pysteps github repository:

• master has been renamed to v1.x.
  This version will no longer be actively developed, but if needed, bug fixes can be backported for users who depend on pysteps-v1.
• xarray/main has been renamed to main.
  All active development will happen in main (which will soon have a tagged v2 release).
  There is no more master branch; to keep with the times, the default branch is now called main.

What to do if you were using the pysteps master branch in scripts / production code:
Please avoid using 'master' as a version in production code; it's better practice to use a release (tagged version, e.g. v1.21.5).
If your goal is really to use the 'development pysteps-v1', please point to the v1.x branch instead. Just like main, this is also a protected branch, so pull requests into this branch also need to be reviewed.

Feel free to react below if you have any comments/feedback/questions!

Best wishes from the Open Nowcasting Hackathon,

Lesley