Give the spec a version?

[DavidBuchanan314]

I don't imagine there'd need to be any significant changes to the core phc-string-format spec going forwards, but just in case, I think it'd be worthwhile to give the spec a version - so a library can say in its documentation that it implements a particular version. To be clear, this would have no impact on the format itself.

Given the relative maturity/completeness of the spec at this point, v1.0.0 feels appropriate (if using semver, in line with C2SP specs)

[tarcieri]

That sounds okay to me as the only person currently maintaining this. It might also make sense to upstream to C2SP.