HTML5 Boilerplate links changed

[Gergely Nagy]

In section Other Resources both urls lead to a 404, seems the structure of h5bp repository changed, documentation folder was moved to its own location:

In the 2 urls its a simple replace from dist/doc to docs. I would say, this change does not need a full blown PR.

The fixed lines would be:

- 📖 [HTML5 Boilerplate Docs: The HTML](https://github.com/h5bp/html5-boilerplate/blob/master/docs/html.md)
- 📖 [HTML5 Boilerplate Docs: Extend and customize](https://github.com/h5bp/html5-boilerplate/blob/master/docs/extend.md)

[Anurag Nishad]

I fix this issue needed approval
Here's the link Of My Commit
e83c991