Make "v" prefix optional by default

[blakjak44]

For those of us that don't want to include a v prefix in our VCS version.

[mtkennerly]

Thanks for your PR. However, this was a deliberate decision, and changing the default now would break backwards compatibility. This is to avoid false positives from tags like 2nd-tradeshow-demo (would become 2) and 2022-04-26-nightly (would become 2022).

That said, I'll consider how to streamline opting out of the v, since it's been a recurring request. For now, please just set a custom pattern.