feat(index): respect executable path for pptr

Respects the "executable path" for puppeteer.

index.js

@@ -24,15 +24,29 @@ const launch = async () => {
     maxConcurrency : 2,
   };
 
+  const puppeteerOptions = {};
+
   if (process.env.CHROME_OPTIONS) {
-    options.puppeteerOptions = {
+    Object.assign(puppeteerOptions, {
       args : process.env.CHROME_OPTIONS.split(' '),
-    };
-
+    });
 
     debug('#launch() using extra launch arguments:', process.env.CHROME_OPTIONS);
   }
 
+  if (process.env.PUPPETEER_EXECUTABLE_PATH) {
+    Object.assign(puppeteerOptions, {
+      executablePath : process.env.PUPPETEER_EXECUTABLE_PATH,
+    });
+
+    debug('#launch() using exeuctable path:', process.env.PUPPETEER_EXECUTABLE_PATH);
+  }
+
+  // merge in options if they were triggered
+  if (Object.entries(puppeteerOptions).length > 0) {
+    options.puppeteerOptions = puppeteerOptions;
+  }
+
   cluster = await Cluster.launch(options);
 
   debug('#launch(): configuring PDF rendering task');