When providing browserEndpoint option, pagedJS correctly connects to it

Issue https://gitlab.pagedmedia.org/tools/pagedjs-cli/issues/42.

1. Passing browserEndpoint from command line args to Printer
2. If the browser is remote, don't send an HTML file to it, but its content.
3. If browser is remote, use puppeteer.connect instead of puppeteer.launch

src/printer.js

@@ -43,13 +43,12 @@ class Printer extends EventEmitter {
 
     if (this.browserWSEndpoint) {
       puppeteerOptions.browserWSEndpoint = this.browserWSEndpoint;
+      this.browser = await puppeteer.connect(puppeteerOptions);
+    } else {
+      this.browser = await puppeteer.launch(puppeteerOptions);
     }
 
-    const browser = await puppeteer.launch(puppeteerOptions);
-
-    this.browser = browser;
-
-    return browser;
+    return this.browser;
   }
 
   async render(input) {