feat!: add metadata to Tag object and update Parse(), Equals() and String()

tagcmp.go

@@ -16,7 +16,7 @@ type Tag struct {
 	MissingPatch bool   // whether or not he patch semver part was left out
 	Suffix       string // tag suffix (e.g. "-alpine") [would be release candidate in semver]
 	UsesV        bool   // whether or not the tag uses the "v" prefix
-	Metadata     bool   // metadata: what's after + and after the first "-"
+	Metadata     string // metadata: what's after + and after the first "-"
 }
 
 // ByTagAsc sorts tags in ascending order where the last element is the latest tag.