item.get_type() does not recognize webm

[manujchandra]

Hi,

When using item.get_type() on a webm file, it returns an enum of 0 and the file is not recognized as ITEM_VIDEO.

Although I have not tested it, we can also test if webp files are being recognized as images.

The following epub can be used for testing.

Thanks.

[aerkalov]

Good point. I guess this extensions mapper could be updated a little bit.