Open the http file system in the wb mode

[pingsutw]

We can only use rb mode in the HTTP file system for now. It will be great if we can support wb mode.

https://github.com/fsspec/filesystem_spec/blob/61cdf52cd0aaf524945ffb83502be39fccaee363/fsspec/implementations/http.py#L350-L351

[martindurant]

Since we do have a pipe using POST or PUT methods, this is perfectly possible. Because the operation would not be multi-part, the whole of the file would need to be buffered and the upload only happens when the file is closed (.flush(final=True)).