[docs] [issue37779] configparser: add documentation about several read() behaviour

[Stéphane Blondon]

Change by Stéphane Blondon <stephane.blondon at gmail.com>:


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keywords: +patch
pull_requests: +14908
stage: needs patch -> patch review
pull_request: https://github.com/python/cpython/pull/15177

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37779>
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