Add support for mix-blend-mode

[MoustafaSVuukle]

I have an SVG file with style attribute containing this mix-blend-mode: multiply and its not rendering it at all. Works in browsers.

[mrbean-bremen]

mix-blend-mode is not implemented at all - I would expect it to render as if it were not set. Do you have an example file (if this is still valid for you) so I can have a look if that is just the missing implementation, or something else?