added offset section, restructured annotations tutorial, reworked

AnchoredOffsetbox section, embedded code that used to link out to
gallery examples, also minor consistency and linking tweaks throughout

Co-authored-by: Jody Klymak <[email protected]>
Co-authored-by: Tim Hoffmann <[email protected]>
Co-authored-by: Elliott Sales de Andrade <[email protected]>
Co-authored-by: Joseph Fox-Rabinovitz <[email protected]>

Author: 5 people