Clarify version handling imgui

[Rookfighter]

@boris-kolpackov
As imgui 1.86.0 is now on cppget.org I want to catch up with the upstream versions 1.87.0 and 1.88.0. However, afaik these versions also contain breaking changes (1.87.0 does not support pre C++ 11 compilers any more), which is - I believe - not in line with semantic versioning. Is there any specific way to handle such situations?

Note: I already started the publishing process for 1.87.0.

[boris-kolpackov]

There is no requirement that packages published to cppget.org follow semver (would have been nice but way too impractical). So I don't think there is anything we can do about upstream's choices except maybe add a note in the appropriate README warning the user that while the version is semver syntactically, it is not semantically.