Add the haystack-experimental package as a dependency

[julian-risch]

The haystack-experimental package should be added as a dependency Haystack. Users then don't need to manually install the experimental features via pip install haystack-experimental but instead automatically have them when they install Haystack.

haystack-experimental should be added here:

haystack/pyproject.toml

Line 42 in 08104e0

dependencies = [

https://github.com/deepset-ai/haystack-experimental