Testing #62976 and #64164

• Windows @dbaeumer
• anyOS @kieferrm

Complexity: 3

Instructions:

• Read https://github.com/Microsoft/vscode-docs/blob/vnext/release-notes/v1_31.md#html-and-css-custom-data-support and understand what it does.
• These two samples should illustrate the usage of the custom data: https://github.com/octref/simple-customdata and https://github.com/octref/svg-data
• Here are the more detailed doc:
  • HTML Custom Data
  • CSS Custom Data

Test the following:

• With html.experimental.customData and css.experimental.customData, you can make VS Code understand custom HTML tags/attributes and custom CSS properties/atDirectives/pseudoClasses/pseudoElements
• You are able to pack the JSON files into an extension using contributes.html.experimental.customData and contributes.css.experimental.customData.