Update README_PL.md

version 1.0 updated to 2.0.0
Merge pull request #66 from electricg/master

Update Italian translation
Merge pull request #65 from lukasz-jakub-adamczuk/patch-3

Update README_PL.md
Fix my twitter handle
Updated portuguese version to 2.0.0
Added 3 JS and 1 CSS

Found a lot of these useful so added some of my own I had come up with.
Add question about null and undefined
Merge pull request #67 from shankarcabus/master

Updated portuguese version to 2.0.0
Merge pull request #69 from castus/patch-1

Add question about null and undefined
add Japanese translation
Merge pull request #71 from toshimaru/japanese

Add Japanese translation
translation error in Chinese edition

translation error in Chinese edition, 工作->工具
Chinese translation of FOUC
doctype is more visualized than its Chinese translation
little fix
Merge pull request #72 from lufeihaidao/master

Chinese edition fix
修正URL
修正URL
修正URL
Merge pull request #74 from joe5yellow/master

Fix URL previewed in GitHub