Add a quickstart guide to documentation

[johnthagen]

For new users transitioning to crypto-browserify (for example due to recent create-react-scripts 5 breakage), it would be really helpful if the user guide had a small example of how to:

• Install crypto-browserify and configure package.json
• How to import and use the package

For example, treating this like a normal npm package, I expected that this could work:

  "dependencies": {
    "crypto-browserify": "^3.12.0",

import hash from "crypto-browserify";

But it does not. Likely this needs to be patched over the "crypto" namespace, but having explicit instructions for this would be helpful.

[m12lrpv]

If no one can use it due to lack of documentation then there really isn't any point in it existing.