Week Input Support

[danieldogeanu]

Hi! First of all, I want to say that I really like your plugin.
I would like to suggest you to implement support for week inputs.
It would be really useful, and I think would make this plugin complete.

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I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report 
[x] Feature request
[ ] Documentation issue or request

Current behavior

• No format for weeks.

Expected behavior

• There should be a ww or Www format for weeks.