Add button style to checkbox

[mdartic]

Related to #3601

I add

• button style to checkbox
• fill, size, textColor props to checkbox-group
• use cases in spec

Tell me if you agree with my PR, and if not what I have to change to make you accept it ?

Hope it will help !

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[mdartic]

Hello @QingWei-Li and @Leopoldthecoder

What do you think of this PR ?

[Leopoldthecoder]

This PR is big enough to be shipped with our next minor version. So we'll come back to this before 1.3.0 release.

[Leopoldthecoder]

Some conflicts came up after #3700. Could you resolve them? Thank you.

[mdartic]

I'm on it to fix and implement new tests.

[mdartic]

Well, after some mistakes with a bad rebase, I think it's ok now.

I add the min/max feature on the checkbox button too, and integrate in on an example of checkbox-group buttons.

Hope it will be ok.

[Leopoldthecoder]

Hi, I'll take a look at this later this week. Thank you for your patience.