formatWeekDay is using wrong date-fns format

[lambert-velir]

Expected behavior

formatWeekDay is supposed to be provided the day of the week as a string, eg, "Friday"

Actual behavior

formatWeekDay is being provided a string of numbers, eg, "0016"

Steps to reproduce

<DatePicker
  selected={this.state.date}
  onChange={date => this.setState({ date })}
  formatWeekDay={d => {
    console.log("D", d)
    return d;
  }}
/>

The problem is that package.json has date-fns v2, which has breaking changes, one of which is the format for the day of the week.

To fix this, either change package.json to use version 1 of date-fns, or update this line to have a format of "EEEE"