Execute webr cells when developing in VS Code or RStudio

Breaking Changes

• We've transitioned to using the {webr-r} code cell designation from our original {webr} designation.
  • The {webr-r} tag allows for code cell evaluation prior to rendering the document
  • Moreover, the {webr-r} component does not need to be registered under the knitr compute engine.

Please update code cells from:

```{webr}

```

To:

```{webr-r}

```