Feature Request: Always upload blob directly instead of sending URL

[shibaobun]

I think the szurubooru useragent is being blocked by Twitter now because I will frequently get Couldn't upload post. Download target returned HTTP 403. (Forbidden) when trying to upload images from Twitter. This could theoretically be mitigated by using directly uploading the blob imagedata already displayed in the preview menu instead of simply sending the URL to szurubooru to redownload again. In addition to working around 403 errors like this, this solution would be lighter on the image source servers since the same image wouldn't need to be redownloaded multiple times.
I may be able to work on this eventually, but I am a bit busy right now so it could take a while

[shibaobun]

So I'm dumb and forgot that I could use [fallback] Upload as content which is exactly what I want, but I'm still interested in better integrating uploading as content for automatically detected websites, i.e. twitter on image 2 and 3.
For anyone else interested in this feature, would a checkbox in the settings like Always upload as content work, or should this be set per-site? Personally, I don't really see the use of uploading as URL when I can upload as content. I'll try to get a PR out with hopefully not the worst code!

[shibaobun]

I added PR #63 for this!

[shibaobun]

Also, I just want to say, thank you so much for making this extension! I download so many images with this on my own booru and it works so well, it's really a killer feature for szurubooru in my opinion 😄