provide mimeType instead of fileName

[mixmix]

I have an application where I'm storing blobs and not storing the filename. I do store a: { title, mimeType, size }
At the moment I'm using render-media by faking a filename, then internally render-media guesses a mimeType from my extension. This feels slightly painful when I can see the API could be extended to just allow mimeType to be passed in directly?

Would this be a welcome addition I'm happy to open a PR.

[fix]

agree on this, most of the time you are able to provide with the right mime type. I think it is possible to make a simple PR that keeps backward compatibility.

That would be ok for you @feross?