Add stylelint plugin link and global command

[srayeskyo3]

2 things that I had to do, might be useful to add to the readme

[sgengler]

@srayeskyo3 looks great! One suggestion for a possible addition as well.

[sgengler]

@srayeskyo3 yes I think this is a good note as this will confuse people

Additionally, instead of installing globally you can also add a script in package.json to run it as well, like:

"scripts": {
    "styelint": "stylelint foo/**/*.scss'",
  ...
}

then run with npm run stylelint or yarn stylelint

would probably be good to add a note for that as well.