gh-106318: Add examples to str method entries

[adorilson]

This PR improvements the str method documentation, adding snippet code in the follows methods and other minor improvements:

• capitalize
• casefold
• center
• count
• encode
• endswith
• expandtabs
• find
• index
• isalnum
• isalpha
• isascii
• isdecimal
• isdigit
• isidentifier
• islower
• isnumeric
• isprintable
• isspace
• istitle
• join
• ljust
• lower
• lstrip
• maketrans
• partition
• replace
• rindex
• rjust
• rpartition
• rsplit
• rstrip
• startswith
• swapcase
• translate
• upper

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📚 Documentation preview 📚: https://cpython-previews--105670.org.readthedocs.build/

• Issue: Add examples to docs for str methods #106318

[hauntsaninja]

Thanks for working on this! Mostly looks good, left a few minor comments

Most non-trivial contributions to CPython have an associated issue that serves as a place for higher level feedback and to track backports. I went ahead and opened one for this change in #106318

[terryjreedy]

I agree with hauntsaninja's comments. Comment changes are required.

I also think most (all?) of the 'For example's could be moved to the end of the previous paragraph, or deleted and only the '::' put at the end of the previous paragraph instead of '.'

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[adorilson]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@terryjreedy: please review the changes made to this pull request.