Azure DevOps and SharePoint Framework (SharePoint#2549)

* spfx azure devops: created the main article page

* azure devops spfx: documented the build process

* azure devops spfx: documenting most of the deployment steps

* azure devops spfx: added variables configuration and results

* Update implement-ci-cd-with-azure-devops.md

azure devops devops: proof reading & editing page content.

* azure devops spfx: fixing typos, refrasing sentence

* azure devops spfx: fixed node installation for spfx steps

* azure spfx devops, fixing linting issue

* azure devops spfx: fixing linting issue

* Update implement-ci-cd-with-azure-devops.md

* azure devops spfx: minor revisions following proof-reading

* azure devops spfx: updated all sequences to node v8 for supportability

* Update implement-ci-cd-with-azure-devops.md

azure devops spfx: proofread/edited Continuous Deployment section.

* azure devops spfx: fixed technical detail following wording review for CD

* azure devops spfx: fixing additional typos

* spfx azure devop: updating office 365 cli command for connecting

Author: baywet