Refactor

1. add 8 secs timeout for SerializeAddon API test
2. move demo page's addons control panel into a single div
3. remove unnecessary config in demo page
4. remove v8-profiler-node8 dependency
5. remove duplicate css option

addons/xterm-addon-serialize/src/SerializeAddon.api.ts

@@ -16,6 +16,7 @@ const height = 600;
 
 describe('SerializeAddon', () => {
   before(async function (): Promise<any> {
+    this.timeout(8 * 1000);
     browser = await puppeteer.launch({
       headless: process.argv.indexOf('--headless') !== -1,
       args: [`--window-size=${width},${height}`]