Add reference to webpack.Compilation to generate

[dirkgroenen]

For one of my projects I'm looking for a "manifest generator" which also adds the integrity of each asset. I've tried many of the available plugins, but none of them really seemed to be doing to job 100% correctly.

Compared to the other available plugins I really like the quality and extendibility of this one. Especially the generate option is very useful and promising.
In order to create the manifest I'm looking for I need some sort of reference to the Webpack compilation object, preferably from within the generate option. Unfortunately this isn't yet available, hence this PR.

Additionally I've also gone my way and added an example to help others solve the same problem. I've noticed there are quite some issues and topics around that try to cover this problem.

This would also close #137

[rndm2]

Is this PR forgotten?

@danethurber are you going to merge this or I should try to find another way to solve my problem?

[rndm2]

I think you should revert changes in this file

[shellscape]

Thanks for opening this PR a while back, and I'm sorry that it didn't get attention sooner. We've landed a major refactor in #222 that has resulted in some significant conflicts. We'll keep #137 open and will implement a fix along these lines, but will likely end up very different.