docs: faq

[cpcloud]

Please describe the issue

A number of questions come up on a somewhat regular basis:

• The behavior of overlapping column names in a join and why in most kinds of joins deduplication is a mistake (Getting started with Ibis on Redshift #1223)
• Why certain expressions like slicing and distinct don't exist on column expressions in Ibis (only on tables) (bug: Integer column not subscriptable #6222)

Code of Conduct

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