Added tileset sharing feature

Good news!

I added a feature that allows sharing and saving your tileset as an url in the form of:

https://quinten.github.io/random-tileset-generator/?selectedcheckeredbg=vbrickcheckeredbg&selectedrandombg=concreterandombg&selectedadvanced=acidadvanced&selectedeasy=acideasy&selectedcheckeredfill=albertcheckeredfill&selectedrandomfill=tildarandomfill&selectedattributes=mushrooms&selectedtopping=grasstopping&bgColor=9c95dc&solidColor=c19ab7&randomColor=228cdb&topColor=087e8b&easyColor=087e8b&attrColor=fac8cd

This will however take you to the github page.

Another cool feature is that you can hit randomize a couple of times and then use the browsers back button to revisit old combinations (also only works with the github served page)