Resource system does not allow keys like "h1"

[mpost]

Problem description

Using a key in a json resource file like "h1" does not work. The schema check states property "h1" is not allowed.

Expected behavior

Any reasonable valid string should be allowed.

Environment

• Tabris.js version: 3.7

Code snippet

{
  "$schema": "../../node_modules/tabris/schema/fonts.json",
  "h1": {
    "size": 96
  }
}

[tbuschto]

This is a reserved key since we may want to support it as an markup element.