Make AddPicture take a slice of bytes or a reader

[martskins]

Having this method take a slice of bytes or a reader, instead of a path, would be extremely helpful.
I'm currently using a fork that has an alternate version of AddPicture that does this so I can use it in a lambda function in AWS (which does not have a file system).

One thing I'm not entirely sure is what is the purpose of this field pic.NvPicPr.CNvPr.Descr = file (that assignmed is found in the addDrawingPicture method. My forked version is working with that assignment commented out, but I'm not sure if it breaks anything else. There are no obvious referrers neither.

If that field isn't exactly needed and having a version of AddPicture that accepts bytes is considered useful, I would be willing to submit a PR or help with the implementation.

[martskins]

should I try and submit a PR for this? my initial idea was to create a new addPictureFromBytes method, so it shouldn't break anything

[dolmen]

I had the same issue, and to workaround I had to create a temporary directory to dump my image file data. This is a dirty hack and I would be happy to drop it.

So I would be very happy if this feature is implemented and I will help with the review of an implementation.

[martskins]

@dolmen I opened a PR, #271, it's basically a copy paste of the original function with some changes to enable passing a slice of bytes. Feel free to comment on it or suggest changes, I didn't really put much time into it as I needed it kinda fast.