Report Within R2 in `pf.etable()`

[s3alfisc]

For compatibility with r-fixest, we would like to report adjusted R2 in pf.etable().

In R, we have

In Python, we have

import pyfixest as pf 
data = pf.get_data()

fit = pf.feols("Y ~ X1 | f1", data = data, weights = "weights")
pf.etable(fit)

To do so, we need to populate the r2_within_list here.

We then add it to the model_stats_df here .

And I hope this would be it! (Though not sure, would have to be tested).

@AronNemeth would you be up for this one? Should be relatively small and self-contained.

[AronNemeth]

Sure thing! I'll get to work on this

[s3alfisc]

Awesome! =)