Improve docs for new textbook dev hires

[philschatz]

Documentation ideas:

• [x] list of tools that we use (oer.exports, docbook, princexml, XSLT, ) https://github.com/Connexions/oer.exports/pull/3023

• [x] how is content entered (CNXML) by CM’s into the platform https://github.com/Connexions/oer.exports/pull/3023

• [x] difference between webview and archive, and legacy https://github.com/openstax/book-tools/blob/master/repositories.md

• [x] you will use the complete zip (url’s) and the collection number (“More Downloads”)

• [x] basic list of GitHub Repos https://github.com/openstax/book-tools/blob/master/repositories.md

• [x] difference between openstax and Connexions GitHub orgs

• [x] Link to examples/config documentation in cnx-recipes https://github.com/Connexions/cnx-recipes/pull/334

• [x] explain philosophy of the current pipeline (Docbook) and why the move to recipes https://github.com/Connexions/oer.exports/pull/3023 (partial explanation)

• [x] blurb about vendors (WW and 6redMarbles, Phillipines)

Need to cover personally

• [ ] GitHub, Pull Requests, command line (merge vs rebase) (say)
• [ ] places to learn more about Terminal, GitHub, Atom, ...