[comp:modal] modal弹窗支持全屏拖动

[lvzero535]

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

弹窗全屏可以拖动

What does the proposed API look like?

给IxModal 加个dragger

<IxModal dragger>
    <p>Some contents...</p>
    <p>Some contents...</p>
    <p>Some contents...</p>
  </IxModal>

[idux-bot]

Translation of this issue:

[Comp: Modal] MODAL pop -up support supports full screen drag

• I have searched the [issues] (https://github.com/iduxfe/idux/isSues) of this repository that this is not a duplicate.

What PROBLEM DOES This Feature Solve?

The pop -up full screen can be dragged

What does the proposed api look like?

Add a drawer to IxMODAL

<IxModal dragger>
    <p>Some contents...</p>
    <p>Some contents...</p>
    <p>Some contents...</p>
  </IxModal>