fix: change README img link to website (#18637)

The main image in the README (browser-vscode) is large and has `cursor: pointer` on it which makes it more likely that people will have the urge to click it like I did.

I expected it to open the website when clicking it, but instead it opens itself on `user-images.githubusercontent` which is pretty pointless.

I just wrapped it in an anchor tag that points to the website instead!

Author: braebo

README.md

@@ -24,7 +24,9 @@ for each task, in the cloud, in seconds. It enables you to describe your dev env
 
 Tightly integrated with GitLab, GitHub, and Bitbucket, Gitpod automatically and continuously prebuilds dev environments for all your branches. As a result, team members can instantly start coding with fresh, ephemeral, and fully-compiled dev environments - no matter if you are building a new feature, want to fix a bug, or do a code review.
 
-![browser-vscode](https://user-images.githubusercontent.com/22498066/135150975-23bba3a6-f099-48c5-83ed-a1a6627ff0e9.png)
+<a href="https://www.gitpod.io">
+  <img src="https://user-images.githubusercontent.com/22498066/135150975-23bba3a6-f099-48c5-83ed-a1a6627ff0e9.png" alt="browser-vscode" />
+</a>
 
 ## Features