Add Posthog tracking + fix extension download + doc

src/app.js

@@ -147,8 +147,9 @@ export function createApp(config, pool) {
     }
 
     const filePath = outputPath(config, job.id, job.targetFormat);
+    const downloadFilename = `${path.parse(job.originalFilename).name}.${job.targetFormat}`;
     res.set('Content-Type', job.outputMimeType);
-    res.set('Content-Disposition', contentDispositionHeader(job.originalFilename));
+    res.set('Content-Disposition', contentDispositionHeader(downloadFilename));
     fs.createReadStream(filePath).pipe(res);
   });