Use single quotes :P

modules/utils/getContentType.js

@@ -1,22 +1,22 @@
-const mime = require("mime");
+const mime = require('mime');
 
 mime.define({
-  "text/plain": [
-    "authors",
-    "changes",
-    "license",
-    "makefile",
-    "patents",
-    "readme",
-    "ts",
-    "flow"
+  'text/plain': [
+    'authors',
+    'changes',
+    'license',
+    'makefile',
+    'patents',
+    'readme',
+    'ts',
+    'flow'
   ]
 });
 
 const textFiles = /\/?(\.[a-z]*rc|\.git[a-z]*|\.[a-z]*ignore|\.lock)$/i;
 
 function getContentType(file) {
-  return textFiles.test(file) ? "text/plain" : mime.lookup(file);
+  return textFiles.test(file) ? 'text/plain' : mime.lookup(file);
 }
 
 module.exports = getContentType;