Please update instructions for building dependencies

[MurKit]

The new version of mozjpeg uses cmake.

imagemin/imagemin-mozjpeg#37
mozilla/mozjpeg#314

Your project is a way for people who are not very familiar with C to use all this.
Could you please update your readme?

I used just

cmake -G"Unix Makefiles"
make 

But maybe for some other users it will be different.

[vannitotaro]

Currently https://github.com/danielgtaylor/jpeg-archive/blob/master/README.md#building says:

./configure --with-jpeg8

so according to https://github.com/mozilla/mozjpeg/blob/master/BUILDING.md#libjpeg-v7-or-v8-apiabi-emulation you must run:

cmake -G"Unix Makefiles" -DWITH_JPEG8=1