Add web front-end and fix API issues

node_modules/yargs/build/lib/yerror.js

@@ -0,0 +1,9 @@
+export class YError extends Error {
+    constructor(msg) {
+        super(msg || 'yargs error');
+        this.name = 'YError';
+        if (Error.captureStackTrace) {
+            Error.captureStackTrace(this, YError);
+        }
+    }
+}