"1.0.0-beta.2" should be less than "1.0.0-beta.11"

[icnocop]

Hi.

Thank you for cpp-semver.

semver::lt("1.0.0-beta.2", "1.0.0-beta.11") should return true, but it returns false.

From https://semver.org:

1.0.0-beta.2 < 1.0.0-beta.11

Related to https://github.com/easz/cpp-semver/issues/7

Thank you.