Added issues with M1 mac and 'npm install' to README

[kitokazu]

As I was following the instructions on how to get my environment setup, I ran into a few issues with bundle install and npm install. After looking into it, the bundle install issue may have been a result of using an M1 mac.

Error with bundle install:

There was an error parsing 'Gemfile': cannot load such file -- em/pure_ruby. Bundler cannot continue

Here is the resource I found that helped. The main command that helped was:

gem install eventmachine --platform ruby

For npm install I had to make sure that my computer was running the version of node that was compatible with the project. Link to source that helped.

I essentially used n which is a Node version manager that can be installed via npm.

npm install -g n   # Install n globally
n <version>         # Install and use <version>

[corejh]

looks good, thanks for the updates. after @d-ahn10 approves, we can merge

[d-ahn10]

Looks good~ Thanks Kai!
Good to see this working on M1 Macs too