Fix autofold imports issue#1208

[malucky]

The original reported issue is that HTML is auto-folded.
But as of this PR, the observed behavior is that nothing
is auto-folded.

Changes:

• configure Monaco setting to folding: true - fixes all
  use cases of
• add autoFold directive to uses

[malucky]

alternative to adding autoFolding directive to all instances of <code-demo-editor> is https://github.com/codelab-fun/codelab/compare/master...malucky:auto-folding-alternative?expand=1

But I don't have confidence this alternative won't break something else

[kirjs]

Hey, thanks for looking into this.

ideally code-demo is a generic component which could be used outside of the codelab, so the first option is preferable.

I think one way to avoid redundancy would be later create a codelab-specific wrapper that would enable autofolding, but I think for now this would be good to be merged as it is.