SCQA / SCQH oriented to external users of diginomics project (i.e. why create diginomics for the world)

[rufuspollock]

This is a sort of follow up to #37 - as discussed with @theo-cox this likely overlaps but is distinct and more focused on what users would get and less on our "internal" motivation for the change.

Acceptance

• Blog post up (either from now or back-posted to jan when we drafted this material) based on SCQA structure (and/or pyramid model https://scqa.lifeitself.org) Here: Create why-diginomics.md #78
• use this content for an about page for the site

Tasks

...

[theo-cox]

@rufuspollock PR for draft is here: #78

Note it is minimally tidied (i.e. without much rewriting from our notes); I wanted to ship a draft to move the ball down the field but after a week of heavy report writing my brain feels too mushy to do rewrites that I'd trust all that much quality wise!