Create a new formula branch.

`formula_branch(..., name = NULL)`

- ...
branch definition expressions.

- name
Name for the new formula.

a `formula_branch`

object.

Other formula branch functions:
`add_formula_branch()`

```
# Define a formula branch.
model_specifications <- formula_branch(
y ~ femininity,
y ~ femininity + hurricane_strength,
y ~ femininity * hurricane_strength
)
# Create a mverse, add the branch.
mv <- create_multiverse(hurricane) %>%
add_formula_branch(model_specifications)
```