feat: add base snippet

Written when reworking a version of my dev landing site (should be
`O(1)`).

src/main.js

@@ -0,0 +1,22 @@
+// NOTE: not using deprecated `keyCode` attribute
+const keySequence = ["ArrowUp", "ArrowUp", "ArrowDown", "ArrowDown", "ArrowLeft", "ArrowRight", "ArrowLeft", "ArrowRight", "b", "a"];
+let sequenceStep = 0;
+
+function callbackFunc() {
+
+}
+
+// TODO: as func to pass to `keydown` listener
+document.addEventListener("keydown", function (e) {
+  console.log(e)
+  if (keySequence[sequenceStep] === e.key) {
+    sequenceStep += 1;
+
+    if (sequenceStep === keySequence.length) {
+      sequenceStep = 0;
+      callbackFunc();
+    }
+  } else {
+    sequenceStep = 0;
+  }
+});