[Feature request] `indefinitize` to get the correct indefinite article?

It would be nice to have a `indefinitize` function to add the correct indefinite article:
```
indefinitize("child") == "a child"
indefinitize("element") == "an element"
indefinitize("universe") == "a universe"
indefinitize("undisclosed recipient") == "an undisclosed recipient"
```
The rules only gets a bit more complicated when dealing with "u" as first letter.