Material Design Introduction link in the README is broken

[rahul-sr]

What is the actual behavior?
The link points to https://material.io/design/material-design/introduction.html
which doesn't work.

What is the expected behavior?
The actual link should be pointing to https://material.io/design/introduction

Submitted the PR for the fix: #5357

[asquenn]

This is Material Design Lite, not normal MD.