Builtin: semver

[shykes]

I am trying to port a Dagger module from Go to Dang, and it calls the golang.org/x/mod/semver package to check if a version string is valid semver. Relevant snippet:

	version := strings.TrimPrefix(tag, "sdk/typescript/")
	versionFlag := strings.TrimPrefix(version, "v")
	if !semver.IsValid(version) {
		versionFlag = "prepatch"
	}

If Dang had a semver builtin, I could port this code without hacky workarounds like building & executing a semver-parsing CLI tool.

[sagikazarmark]

@vito I'd like to take a stab at this if you are open to adding it back

[vito]

@shykes should this be a Dagger core API? 🤔

Not against putting it in stdlib but figured I'd raise since Dang stdlib vs. Core is something we've gone back and forth on for other ideas, and I saw you had a version related proposal, maybe there's overlap (only skimmed)