docs: update getting start view container style

Author: damingerdai

packages/dev-app/src/app/pages/getting-started/getting-started.component.html

@@ -3,7 +3,7 @@
     loading
 </div>
 } @else {
-    <div class="container m-auto">
-        <div [innerHTML]="markdownContent"></div>
+    <div class="d-flex justify-content-center">
+        <div class="markdown-content" [innerHTML]="markdownContent"></div>
     </div>
 }

packages/dev-app/src/app/pages/getting-started/getting-started.component.scss

@@ -0,0 +1,8 @@
+.markdown-content {
+    margin {
+        top: 32px;
+        left: 32px;
+        right: 32px;
+    }
+    max-width: 400px;
+}