Project Euler : add solution for problem 18 (Max Path Sum I) + test.

Project-Euler/test/Problem018.test.js

@@ -0,0 +1,18 @@
+import { maxPathSum } from '../Problem018'
+
+const example = `
+3
+7 4
+2 4 6
+8 5 9 3
+`
+
+describe('Check Problem 18 - Maximum path sum I', () => {
+  it('Check example', () => {
+    expect(maxPathSum(triangle)).toBe(23)
+  })
+
+  it('Check solution', () => {
+    expect(maxPathSum()).toBe(1074)
+  })
+})