Clarify in the README how this relates to the new built-in feature to preview HTML files

[thernstig]

VS Code 1.121 was just released with "Quickly open HTML files in the Integrated Browser".

This effectively removes the need for this extension in many cases. But maybe not for all?

I think the README should have an update mentioning instead what value this extension adds on top of the built-in ability to open HTML files. It might even be so that this extension is of much less value and should be deprecated?

[iamart]

I went to delete this extension only to realize it is from microsoft themselves and now there are 2 ways to preview. 🤦🏼