refactor(helper): update module path and function names

- move `helper` package files to root `helper` directory
- update all helper imports
- rename `GetLines` to `getLines` for consistent naming convention

🤖

helper/math.go

@@ -0,0 +1,9 @@
+package helper
+
+func Abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+
+	return x
+}