Add numeric p-value to gam summary table using flextable

Question

I'm just trying to print a nice table using the flextable package. In general flextable works very well, but I need to add a numeric p-value next to the asterisk symbols for significance. Flextable do that automatically for linear models, but it seems that don't do the same for GAM models.

I'm using the mgcv package for gam, and this is what I'm doing:

ab<-gamSim(eg=1,n=400,dist="normal",scale=2,verbose=TRUE)
 
gam_ab<-gam(y~x0+x1+x2, data=ab)
 
summary(gam_ab)
 
as_flextable(gam_ab)

And this is what I get:

Is there any way to add this numerical value in this column for GAM summary tables using flextable? or, is there another easy way to do nice tables for GAM summary? Thank you in advance!