fix bug: node.files.add do not accept object

[tiagochen]

file: src\core\components\files.js
line: 199
api: add
problem: add api's param do not accept object, use Buffer instead

[JonKrone]

@tiagochen Thanks for the PR! And on the ipfs-101 example no less.

Would you please also update the README with these changes?

Also want to make sure @diasdavid is okay with the change from { path, content } to Buffer(content) rather than [ { path, content } ]. This example needs a change either way: #1256

[daviddias]

This was a regression, fix here: #1257. My apologies for the troubles.