Docs: Extend installation instructions

[MichaelCurrin]

Add to install instructions.

Link to the Yarn page which has install instructions on it.

And then a command npm install -g npx to install npx. Or the yarn equivalent if yarn will install npx.

Give both routes for devs - the yarn route and the npm route

[shailen-naidoo]

@MichaelCurrin Thanks for this! npx is a default package installed with newer versions of NPM that allows you to execute local packages

[shailen-naidoo]

In-depth installation guide

[shailen-naidoo]

@MichaelCurrin Working on the enhancement!