Add Edge target and adapt options page to Edge

Now the extension can be built with Edge as a target. This change also
adapts the option page for Edge so it doesn't have a horizontal
scrollbar.

Fixed: translateselectedtext:6
Change-Id: Ie0a38b85d1c604610942b00269004c51fc02963d
diff --git a/src/options/options.js b/src/options/options.js
index 4ee6e35..ec50b6a 100644
--- a/src/options/options.js
+++ b/src/options/options.js
@@ -7,6 +7,23 @@
 
 import {SHARED_STYLES} from './shared/shared-styles.js';
 
+let bodyStyles = document.createElement('style');
+// #!if browser_target == 'chromium'
+let widthProperty = 'width: 470px;';
+// #!else
+let widthProperty = '';
+// #!endif
+bodyStyles.textContent = `
+  body {
+    margin: 0;
+    padding: 0;
+    font-size: 90%;
+    ${widthProperty}
+  }
+`;
+
+document.head.append(bodyStyles);
+
 export class OptionsPage extends LitElement {
   static properties = {
     _storageData: {type: Object, state: true},