[UI] Support UI Automation Test

[YongseopKim]

Now lots of code in ONE-vscode is related to UI. If there is UI automation test system, it would be great.

To get it, we could use cypress and code-server and web test for cross-platform. And also Jest Snapshot Testing.

The automation test will be a mixture of the above.

FYI, cypress and code-server can be referenced here (https://github.com/Samsung/ONE-vscode/issues/336).

[YongseopKim]

The points to be considered

• Cypress and code-server
  • How many parts to support for vscode?
  • CI can integrate this?
• Jest Snapshot Testing
  • ONE-vscode uses Mocha as the test framework but Jest is also a test framework.
  • Will we append it? or introduce a new feature like Jest's feature?

[YongseopKim]

And advice from @lemmaa,

• Now ONE-vscode's UI will have a lot of changes. It cannot be avoided.
• So it would be a good time when almost UI codes are landed.

[YongseopKim]

/cc @Samsung/one-vscode