[Doc] Add OpenMMLab website and platform links
<div align="center">
<img src="resources/mmediting-logo.png" width="500px"/>
+ <div>&nbsp;</div>
+ <div align="center">
+ <b><font size="5">OpenMMLab website</font></b>
+ <sup>
+ <a href="https://openmmlab.com">
+ <i><font size="4">HOT</font></i>
+ </a>
+ </sup>
+ &nbsp;&nbsp;&nbsp;&nbsp;
+ <b><font size="5">OpenMMLab platform</font></b>
+ <sup>
+ <a href="https://platform.openmmlab.com">
+ <i><font size="4">TRY IT OUT</font></i>
+ </a>
+ </sup>
+ </div>
+ <div>&nbsp;</div>
</div>
## Introduction
