. in predictor variable name causes errors

```
dat <- tibble(x.x = 1:10,
y = rnorm(x.x)) %>%
as.data.frame()

mod <- lm(y ~ x.x, data = dat)

a <- qi_builder(mod,
newdata = dat,
slim = FALSE,
ci = 1
)
```

Causes the error

```
Error in possible_interaction_terms(fitted_names, n = k) :
Number of possible interaction terms cannot exceed number of base terms.
```

If I replace the . with a _, the error goes away.