Fix VR mode handling in plugin

[keilyn3d]

Add VR mode handling to html2canvas plugin to read DOM state and avoid caching and requestAnimationFrame.

• src/index.ts

  • Add vrMode option to ContextOptions.
  • Update renderElement function to handle VR mode.

• src/core/cache-storage.ts

  • Add condition to bypass caching when in VR mode.
  • Update addImage and match methods to handle VR mode.

• src/core/context.ts

  • Add vrMode flag to Context class.
  • Update constructor to accept a VR mode parameter.

• src/tests/index.ts

  • Add tests to verify the plugin's behavior in VR mode.
  • Update existing tests to handle VR mode.