Create instructions for running hugo and npm watch at the same time for dev

[autumnfound]

We should document dev process to have watch running with hugo in a way that doesn't crash Hugo. We've had this in the past but it was never documented.

[autumnfound]

@linkfang you were showing me how you had both running at the same time. Did you have to restart hugo on CSS changes, or when renaming files?

[linkfang]

@autumnfound , no need to restart hugo on CSS changes.
But do need to do so when there is a CSS error, like lacking a semi-colon in CSS, etc. Almost all kinds of CSS error will need to restart hugo.

[autumnfound]

@linkfang would you like to take a stab at the documentation for this? It's an easy enough task, and I know you use this sometimes when developing!

[linkfang]

@linkfang would you like to take a stab at the documentation for this? It's an easy enough task, and I know you use this sometimes when developing!

I tested with hugo-solstice-theme project. It seems that we don't need npm watch in this project, as it only uses CSS and can detect the CSS changes and then rebuilt the site.

I think npm watch is only needed for the projects that are using .less files. So, should I update the readme file for all those projects?

[autumnfound]

Nope! That doesn't belong there really. We could put it there, but I'd recommend adding it here as a central place for recommendations when developing. This is more of a "how do we develop with this theme" then how do we use it on a particular site. Does that make sense?

Also, DRY. Dont Repeat Yourself ;) It makes updating docs much harder