SemVer Policy

[pinkforest]

Related: ucan-wg/rs-ucan#48, ucan-wg/rs-ucan#51

Example:
e.g. https://github.com/dalek-cryptography/curve25519-dalek/pull/443/files?short_path=b335630#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5

I would perhaps maybe ask these questions:

1. MSRV Requirement #23 - What happens when MSRV is bumped ?
2. Are there any "stable API" dependencies exposed via Public API and what happens upon breaking changes ?
3. Are there any "unstable API" dependencies exposed via public API similar to ^ ?

[zeeshanlakhani]

@pinkforest any good examples from other libs that have a policy write-up?