Added Image Shrink module

Basically, the image shrink module lets users choose a maximum image size for imgur images if they don't want to have to load extremely large images. For instance, a 5000px wide image of a few words doesn't need to be loaded when it can be seen perfectly fine at 1024px. It uses imgur's thumbnails, specified here: https://api.imgur.com/models/image#thumbs. Whenever an image is shrunken, a link to the original image is added to the post as well.
Not super thoroughly, but it's worked in all the test cases I've used. Also, this shouldn't be a problem if imgur does change the hash length, as it dynamically appends the URL modifier based on where the .extension is. @andytuba recommended modifying the showImages.js module, and I was doing so until I came across a problem: https://github.com/honestbleeps/Reddit-Enhancement-Suite/issues/1507
Anyways, I personally don't have the fastest internet connection and I'm sure many others don't. Loading pictures bigger than my screen is really quite silly and I feel that, if we spread the word a bit, a lot of people would use this feature.

Thanks!