Update documentation from templates processing

[hcdias]

Add save() and saveAs() methods documentations

Description

The docs from save() and saveAs() are nonexistent. Adding them to the docs.

Fixes # (issue)

Checklist:

• I have run composer run-script check --timeout=0 and no errors were reported
• The new code is covered by unit tests (check build/coverage for coverage report)
• I have updated the documentation to describe the changes

[coveralls]

Coverage remained the same at 94.619% when pulling 4de892d on hcdias:patch-1 into b8346af on PHPOffice:master.