WIP @ section 3, 4(WIP), 5, and 7(WIP) of the SMCS (#816)

* Adding outline for section 3 of the cheatsheet, updating #124

* change order and scope

* WIP @ section 3 ,please DO NOT MERGE

* WIP @ secrets maangement

* WIP @ secion 3 for #124

* Fix last markdown issues

* Pre-reserving

* small fixes

* quick update on CI/CD secrets

* adding footnotes

* quick addition

* Add outline for cloud

* Add to section 4

* updated section 3 again

* first final version of chatper 3:

* rewrote first paragraphs of chapter 5

* adding last part

* added missing links

* first version of chapter 5 rewritten

* Added structure for 12 at #124

* Wip @section 7 for #124 and reserved some sections to other github handles (@bendehaan and @thatsjet)

* Add services to use to section 4

Co-authored-by: Ben de Haan <[email protected]>