Fix process is not defined issue

src/browser/index.js

@@ -105,7 +105,7 @@ const downloadFile = (path, blob) => {
  */
 exports.defaultOptions = {
   ...defaultOptions,
-  workerPath: process.env.TESS_ENV === 'development'
+  workerPath: (typeof process !== 'undefined' && process.env.TESS_ENV === 'development')
     ? resolveURL(`/dist/worker.dev.js?nocache=${Math.random().toString(36).slice(3)}`)
     : `https://unpkg.com/tesseract.js@v${version}/dist/worker.min.js`,
   /*

src/common/TesseractWorker.js

@@ -8,7 +8,7 @@
  * @author Jerome Wu <jeromewus@gmail.com>
  */
 const check = require('check-types');
-const resolveURL = process.browser ? require('resolve-url') : s => s;
+const resolveURL = (typeof window !== 'undefined' && typeof window.document !== 'undefined') ? require('resolve-url') : s => s;
 const adapter = require('../node');
 const circularize = require('./circularize');
 const TesseractJob = require('./TesseractJob');