[Feature Request]: Multi-Period DiD for Repeated Cross-Sectional Data

[SvenKlaassen]

Describe the feature you want to propose or implement

Extend DoubleMLDIDMulti for repeated Cross Sections

Analogous to #309

Added

• make_did_cs_CS2021 dgp (subsamples data from make_did_CS2021)
• DoubleMLDIDCSBinary analog to DoubleMLDIDBinary
• DoubleMLDIDCSMulti analog to DoubleMLDIDMulti