https://github.com/Microsoft/pxt-maker/blob/master/docs/boards/SUMMARY.md

**Describe the bug**
URL all 404 not found 

**To Reproduce**
Steps to reproduce the behavior:
1. Go to '[https://github.com/Microsoft/pxt-maker/blob/master/docs/boards/SUMMARY.md](https://github.com/Microsoft/pxt-maker/blob/master/docs/boards/SUMMARY.md)'
2. Click on Any URL. 
3.  See error :  404 

**Expected behavior**
URL incorrect . 
