Fix vertical scrolling of descriptions

[zothynine]

This commit is a bugfix for the issue #130 in CSS. The description text was not scrollable when on left, right or bottom position. I added this CSS:

.gslide-description {
    max-height: 100vh;
    overflow-y: auto;
    …
}

I sadly could not test this on IE11, since I'm working on a Mac,sorry!

[biati-digital]

Thank you for the pull request, i think the bug it's more complex than the provided solution, the content should not be bigger than the image, it should maintain the same height as the image and resize accordingly.

[zothynine]

Thank you for your quick response. I made a second commit in this branch that addresses the height problem. Please review my changes and tell me if they are OK.

Greetings from Vienna, Mario

[biati-digital]

Awesome, seems to be working fine. Thank you for taking the time to fix this.