Add example for excel to json with mapper from file and add docker support

examples/excel2json/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "excel2json",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "Sambo Chea <sombochea@cubetiqs.com>",
+  "license": "MIT",
+  "dependencies": {
+    "xlsx": "^0.16.9"
+  }
+}