semver.bump_prerelease on *-rc9 results in lower version #460

Which version of Python is the problem with?

3.8

What semver version are you using?

No response

What OS are you using? (Add more in the Environment section)

macOS

Situation

When calling semver.bump_prerelease on a version with a prerelease of -rc9, it gets bumped to -rc10. However. according to the semver spec (https://semver.org/#spec-item-11 section 11.4 items 1+2), 'rc9' is considered a string and will be compared to 'rc10' using ASCII sort order, which considers 'rc10' to be lower than 'rc9'.

How to reproduce

>>> import semver
>>> version1 = '1.0.0-rc9'
>>> version2 = semver.bump_prerelease(version1)
>>> version2
'1.0.0-rc10'
>>> semver.compare(version1, version2)
1

Expected behavior

Not entirely sure how the bump_prerelease version should behalve when it gets rc9. ASCII-wise, after 9 you could consider a, but you get rca, rcb which feels a bit odd. Another option could be that the function just returns some kind of error, indicating it cannot determine how to increase rc9 to a higher value.

Environment

No response