feat: error for when there is more source code than parsed

pkg/saccharine/tokenizer.go

@@ -70,8 +70,8 @@ func getToken(i *iterator.Iterator[rune]) (*token.Token, error) {
 }
 
 // Parses a list of runes into tokens. All error encountered are returned, as well.
-func GetTokens(input []rune) (*iterator.Iterator[token.Token], error) {
-	i := iterator.Of(input)
+func GetTokens(input string) ([]token.Token, error) {
+	i := iterator.Of([]rune(input))
 	tokens := []token.Token{}
 	errorList := []error{}
 
@@ -84,5 +84,5 @@ func GetTokens(input []rune) (*iterator.Iterator[token.Token], error) {
 		}
 	}
 
-	return iterator.Of(tokens), errors.Join(errorList...)
+	return tokens, errors.Join(errorList...)
 }