Add web front-end and fix API issues

node_modules/rxjs/dist/cjs/internal/observable/concat.js

@@ -0,0 +1,15 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.concat = void 0;
+var concatAll_1 = require("../operators/concatAll");
+var args_1 = require("../util/args");
+var from_1 = require("./from");
+function concat() {
+    var args = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i] = arguments[_i];
+    }
+    return concatAll_1.concatAll()(from_1.from(args, args_1.popScheduler(args)));
+}
+exports.concat = concat;
+//# sourceMappingURL=concat.js.map