Docs: merge 'Core Concepts' and 'Architecture' in 'How OSO Works'

[ccerv1]

@ryscheng I think my latest version of the docs have a nice flow from schemas to impact metrics to impact vectors. It would be great if you could take a fresh look at the index.mdx file ("core concepts") and merge it with the architecture file.

I think the narrative is along the lines of:

• what we mean by open source / open data / open infra
• everything we care about is cataloged in oss-directory as a project, collection or artifact
• we have an awesome indexing and ci/cd suite that grabs event data from there
• we have an open data pipeline that lets anyone transform data into impact metrics
• we have a community of data scientists and funders who are motivated to make sense and give value to these metrics
• we have a suite of integrations and even a no-code dashboarding tool to bring these insights to the masses

[ryscheng]

I'll take a look, I can def add some color around those concepts, but IMO it's best to keep the architecture of the data model separate from the architecture of the technical infra.