add recordPicker stubs (#322)

src/lightning-stubs/recordPicker/recordPicker.html

@@ -0,0 +1,7 @@
+<!--
+Copyright (c) 2018, salesforce.com, inc.
+All rights reserved.
+SPDX-License-Identifier: MIT
+For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+-->
+<template></template>

src/lightning-stubs/recordPicker/recordPicker.js

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2018, salesforce.com, inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+import { LightningElement, api } from 'lwc';
+
+export default class RecordPicker extends LightningElement {
+    @api displayInfo;
+    @api filter;
+    @api label;
+    @api matchingInfo;
+    @api objectApiName;
+    @api placeholder;
+    @api required;
+    @api value;
+    @api variant;
+    @api checkValidity() {}
+    @api reportValidity() {}
+    @api setCustomValidity() {}
+}