ssb: Add a manual theme color picker.

apps/ssb/tf-news.js

@@ -1,6 +1,6 @@
 import {LitElement, html, unsafeHTML, repeat, until} from './lit-all.min.js';
 import * as tfrpc from '/static/tfrpc.js';
-import {styles} from './tf-styles.js';
+import {styles, generate_theme} from './tf-styles.js';
 
 class TfNewsElement extends LitElement {
 	static get properties() {
@@ -231,6 +231,9 @@ class TfNewsElement extends LitElement {
 			}
 		}
 		return html`
+			<style>
+				${generate_theme()}
+			</style>
 			<div>
 				${repeat(
 					final_messages,