New Content: New developer onboarding

**Why is this content needed**
We maintain our own onboarding material for new devs, but it would be good to centralize this so all the companies could at least refer to this to create their own guides.

**Who will benifit,**
New devs.

**Are you able and willing to create the content**
We might have some stuff we could donate, just adding this issue for tracking this so i don't forget.

