[Steps]: Change title property type to allow react node.

[mytharcher]

When use React component in the title property of Steps component, there will be a warning. This type limitation is not necessary and makes a lot inconvenience. So I remove the type limitation to allow React component in title.

• Make sure you are merging your commits to master branch.
• Add some descriptions and refer relative issues for you PR.
• Rebase your commits to make your pull request meaningful.
• Make sure that your changes pass npm test, npm run lint and npm run build.

Changes in this pull request