feat(docs): Add install instructions for postgres

docs/assets/scripts/tabs.ts

@@ -41,10 +41,12 @@ function groupTabs(tabs: HTMLDivElement[]): TabGroup[] {
             let nextSibling = next.nextElementSibling;
             while (nextSibling === remainingTabs[0]) {
                 if (nextSibling) {
+                    next = remainingTabs.shift();
                     // tslint:disable-next-line:no-non-null-assertion
-                    group.push(remainingTabs.shift()!);
+                    group.push(next!);
                 }
-                nextSibling = next.nextElementSibling;
+                // tslint:disable-next-line:no-non-null-assertion
+                nextSibling = next!.nextElementSibling;
             }
             tabGroups.push(group);
         }

docs/assets/styles/_shortcodes.scss

@@ -112,6 +112,7 @@
             color: $gray-600;
             border: none;
             padding: 3px 6px;
+            margin: 0 3px;
             border-bottom: 2px solid transparent;
             background: none;
             &.active {

docs/content/docs/getting-started.md

@@ -38,6 +38,18 @@ $ npm install mysql
 # or with Yarn
 $ yarn add mysql
 
+```
+{{% /tab %}}
+{{% tab "PostgreSQL" %}}
+You'll need a PostgreSQL server available to your local machine.
+
+In addition, you must install the [pg driver](https://www.npmjs.com/package/pg) for Node.js:
+```bash
+$ npm install pg
+
+# or with Yarn
+$ yarn add pg
+
 ```
 {{% /tab %}}