Support leading v syntax in version strings

[kaedys]

Problem description
Version strings that use a leading v, as in v1.2.3, are a very common format in software versioning, making it clear that the number indicated is a version tag. Authors sometimes either prefer to use this style, or do so forgetfully.

Specifically, one of the mods I use, TargetingModes, updated their version tag to <version>v2.1.0</version>, which is now throwing parse errors.

Describe the solution
Tolerate a leading v on version strings. If the first character is a v, discard it and treat the remainder as a normal semantic version using the existing logic.

Alternatives
Don't believe there is an alternative, other than the existing state, which simply expects all developers to remember to conform to this versioning style. I understand that Microsoft, when writing the .NET standard, did not embrace a leading v, but that doesn't necessarily imply that Mod Manager can't or shouldn't.

Additional materials
It's worth noting that I'm not the author of the offending Manifest.xml. I'm also sure that while this is almost assuredly not an isolated incident, it's also probably not that common. I hope. But it feels like the type of flexibility a mod management application should have. v prefixes are very very very very common in software versioning, and I feel like it makes sense to support that versioning style.

For reference, here's the commit in question. The original author of the mod stepped away, and OdysseyScorpio took it over, which is likely why the versioning scheme changed.