Consider updating README

[tpage99]

Add the walkthrough Youtube video and process for npm run css before commit and PR. I had to go and find the video (forgot where it was and had to find in the slack) and then skim through it to remember the command - just since I'm not used to that being part of my workflow (being a solo dev creates loads of bad habits for me...).

This could be a good issue for someone wanting to contribute or who is a total newbie or someone who just wants another PR for hacktoberfest. We could also have some contributing guidelines or workflow process (create a new branch, set upstream, git fetch, etc.).

[tpage99]

also, in relation to hacktoberfest, it is opt-in now: https://hacktoberfest.digitalocean.com/hacktoberfest-update