Follow semantic versioning

[kkiermasz]

Hey there!

Since the Lottie supports an SPM I think it's safe to say that we should follow its rules. One of them relates to the versioning of libraries. In the documentation we can find below quote:

A package version consists of three integers separated by periods, for example 1.0.0. It must conform to the semantic versioning standard in order to ensure that your package behaves in a predictable manner once developers update their package dependency to a newer version.

Latest release (3.5.0) includes #1420, which is not backward-compatible.

I assume that the dangers of such a release are clear, but if you need more information regarding this, just let me know :)
Because of the above, I just wanted to start the discussion about sticking to semver convention.