Missing

1. Missing explanation
In 
doc/source/tutorial.rst 
    line 102 
AND in 
b2sdk/api.py 
    line 194 
there are mentions of "CORS rules" which are not explained anywhere.
Nothing in doc/source/glossary.rst either. 
Proposed fix: add to glossary, if possible, add to on-hover

2. Missing explanation
In 
doc/source/tutorial.rst 
    line 102
AND in 
b2sdk/api.py 
    line 195
there are mentions of "bucket lifecycle rules" which are not explained anywhere.
Nothing in doc/source/glossary.rst either.
Proposed fix: add to glossary, if possible, add to on-hover

3. Dead link
doc/source/quick_start.rst
    line 77:
"""
    To learn more about sync, see `Sync <sync.html>`_.
"""