Wording about A.B.C number

> A package version number **SHOULD** have the form _A.B.C_, and **MAY**
> optionally have any number of additional components, for example 2.1.0.4
> (in this case, _A_=2, _B_=1, _C=0_). This policy defines the meaning of
> the first three components _A-C_, the other components can be used in
> any way the package maintainer sees fit.

This should mention that version could be e.g. just `1`, but than it means that following components are `0`, for example `example-package-1`. Probably also that one **MUST NOT** release `example-package-1` and `example-package-1.0` (Does `hackage-server` enforce this?)

Start with the quoted package-version wording in this issue and inspect the surrounding PVP specification context. Determine how shortened versions such as 1 should be interpreted, whether 1 and 1.0 must be treated as equivalent releases, and whether hackage-server enforces that distinction; update the specification once those points are settled.

Written by the indexing model from the issue text.