Update README.md to reflect state of native UI

[JDaance]

This PR is a bit tongue in cheek, I spent quite a bit of time migrating to the native version, in part due to this text of deprecation. The native version is not the same as this extension and more, its different, is currently missing support for autorun, and I really missed the scroll bar indicators :). If I would be blunt I would say that the native version is in a beta state, and I had many perceived performance problems, but opinions differ. I hope this extension lives on!

For reference, this is a list of my filed tickets on the native version: https://github.com/microsoft/vscode/issues?q=author%3Ajdaance+
And the general ticket on missing auto run: microsoft/vscode#134941

I did not file all my complaints about it, I just tried to work with it until I gave up and reverted back to this extension.

[hbenl]

I'm actually considering removing the deprecation notice because after initially having high hopes for native testing I'm now fairly disappointed by the state in which Microsoft left it.
FWIW the feature that I am missing is "retiring" tests, i.e. when you change a source file after running tests, the test results will be shown grayed out, so you can see what the last results were but also that they are outdated. I have some test suites that take a long time to run and this feature is very important to me in that situation.

I hope this extension lives on!

Don't worry, it will!

[ralfhandl]

The hint on autorun would have saved me some time, and it is why I switched back to the old UI.