DSK limited to 80 sectors

[TFHFony]

.DSK emulation is limited to 720Kbyte / 80 sectors. Non-Standard disks that use the 81st or 82nd sector cannot be loaded as a disk image.
Example: https://download.file-hunter.com/Games/MSX2/DSK/Dummieland%20(1994)(Soksoft)(Disk%201%20of%202).zip

The use of extra sectors is quite common, also as a copy-protection.
I've also requested the support of .DMK images (#66) which could help running this kind of disks.

[NullPointerReference]

This is possibly a quick-win; by changing:

WebMSX/src/main/room/disk/DiskImages.js

Line 546 in 122834b

this.MEDIA_TYPE_VALID_SIZES = [ 737280, 655360, 368640, 327680, 184320, 163840 ]; // All supported floppy formats

to: this.MEDIA_TYPE_VALID_SIZES = [ 755712, 746496, 737280, 655360, 377856, 373248, 368640, 327680, 184320, 163840]

I.e. adding the length for double-sided, 82, 81 tracks and single-sided 82 and 81 disk-image sizes (in that) order.
This seems to work with the provided example file

[NullPointerReference]

PS: Also tested this on file-hunter.com (thanks @TFHFony) and it seems to work as intended with the given example(s). Note that the proposed 'quick-win' only supports this for Double-density single- AND double-sided images; and did not extend the format to the 184320 and 163840 sizes/formats as I'm unfamiliar with these ...