Passing custom `ddf` to `tidy.svyglm()`

[larmarange]

That issue was already mentioned here: #1096 and also appeared here: ddsjoberg/gtsummary#1913

You can specify a custom Denominator degrees of freedom for p-values and for confidence intervals. This parameter is called ddf in confint.svyglm() and df.resid in summary.svyglm().

In the current version of tidy.svyglm() additional arguments can be passed only to confint() but not to summary(). It would be relevant to have here a dedicated argument that would be passed both to summary() (as df.resid) and to confint() (as ddf).