update README redocly.yaml example to match latest version

[dverbovyi]

Hi, the tool is pretty awesome, keep up the good work!

This is my first experience and I've just playing it around.

I was trying to follow the description inside vs-code after extension installation. The extension didn't prompt me to create .readocly.yaml, so I did it manually by copy-pasting the content from the example, which seems isn't up to date, as I got this:

The correct version of example I found by browsing thought the website

We all often forget to update our docs, so I hope this PR will be useful 😁

[RomanHotsiy]

Thanks, @dverbovyi!

[RomanHotsiy]

@dverbovyi could you actually update it a bit more by changing .redocly.yaml to redocly.yaml (the one with the dot is legacy).

Thanks. We can update it ourselves too.

cc @tatomyr

[dverbovyi]

sure, updated

you're welcome