test: add eslint config validation

test/test-file.ts

@@ -0,0 +1,12 @@
+/**
+ * Simple TS source file to get linted
+ * Can be used to verify new/changed rule behavior
+ */
+function addNumbers(a: number, b: number) {
+  return a + b;
+}
+
+const sum: number = addNumbers(10, 15);
+
+// eslint-disable-next-line no-console
+console.log('Sum of the two numbers is: ' + sum);