feat: 增加Modal的props声明

[RyanLiu0235]

First of all, thank you for your contribution! :-)

Please makes sure that these checkboxes are checked before submitting your PR, thank you!

• [x] Rebase before creating a PR to keep commit history clear.
• [x] Add some descriptions and refer relative issues for you PR.

Extra checklist:

if isNewFeature :

• [ ] Update API docs for the component.
• [ ] Update/Add demo to demonstrate new feature.
• [ ] Update TypeScript definition for the component.