Adding once a minute to examples on main page documentation

[nkinar]

Would it be possible to add an example for once a minute to the main page documentation? In the table, perhaps a string such as

"0 * * * * ?"

I feel that this would be very helpful in the main documentation. Thanks for your great library.

[PerMalmberg]

Sure, make a PR.

[nkinar]

Here is the PR. Thanks for the opportunity to contribute to the documentation.

#37