### What?
This log was appearing when the DatePicker loaded without a registered
locale:
```
A locale object was not found for the provided string ["enUS"].
```
Also fixes css misalignment of icons inside date picker field
### Why?
If i`18n.dateFNS` had not loaded, we were registering the locale with an
undefined value.
### How?
Only register the locale for react-datepicker if i18n.dateFNS is
present.
6ffd4c7825