[Suggestion] add guide for containers(docker) and ci

[vitoyucepi]

Summary

After update I've researched how to build my project in container using gitlab-ci.
To build my project I have to build binary dependencies since image-webpack-loader@7.0.0 because gifsicle-bin have no prebuilt binaries.
I've checked:

• node:12-buster
• node:12-buster-slim
• node:12-stretch
• node:12-stretch-slim
• node:12-alpine
• node:12-alpine3.9

My prepare script benchmark results:

1. node:12-buster-slim
node:12-stretch-slim
   exec time: 3 minutes
   Prepare script:

   apt-get update
   apt-get install -y --no-install-recommends autoconf automake g++ libpng-dev make

2. node:12-buster
node:12-stretch
   exec time: 3 minutes 30 seconds
   Prepare script: NO
3. node:12-alpine
node:12-alpine3.9
   exec time: 4 minutes 20 seconds
   Prepare script:

   apk add --no-cache autoconf automake file g++ libtool make nasm libpng-dev

Why alpine is slow

There's no prebuilt binary packages for musl.

Why buster(stretch) is slower than buster-slim(stretch-slim)

Full debian version is about 6x larger than slim version.

My request

Add prepare scripts to readme or create wiki page for that.

Additional info

imagemin/imagemin-gifsicle#32
imagemin/imagemin-gifsicle#40
imagemin/gifsicle-bin#79
imagemin/gifsicle-bin#113
imagemin/mozjpeg-bin#47
imagemin/optipng-bin#110

[tcoopman]

Can you create a PR for this?

[vitoyucepi]

@tcoopman should I create PR for README.md, another .md file or wiki page?

[tcoopman]

We don't have a wiki so far, so add it to the readme, we can refactor later if it would be too long

[tcoopman]

closed via: #266