ApiDOM Playground - enhancements

[char0n]

The demo is comming and we need to get ApiDOM Playground into fully workable state.

Todo:

• OAS 3.1: all current features needs to work seamlessly
• AsyncApi 2.0: all current features needs to work seamlessly
• resolving and dereferencing should only be enabled if baseURI is provided
• S-expression interpretation should be added