New page: 'What is a content designer?'

Creation of 'What is a content designer?' for the team section of the manual
Rename content-designer to content-designer.md
Update content-designer.md
Create content-designer-jd.md
Update content-designer.md
Update content-designer.md
Update content-designer.md
Update content-designer-jd.md
Update content-designer-jd.md
Merge pull request #114 from gds-padma/patch-1

Grand. Some edits to make, but will merge first and branch on @alextea's advice.