Issue Type: Bug

try and change the "accessibility" setting via keyboard.
When you tab to the setting, NVDA comes out of application mode back to document mode. However, there is no button, link, checkbox, or radio button to interact with. Forcing it back to application mode via insert+spaceBar seems to lose focus.

Part of the issue is that the screen reader can't seem to stay in one mode. This is not a website, so it should stay in application mode throughout. Using a role of application on "main" would force this. In general, this is a bad idea, but this is a true application, so application mode is probably warrented.

Another issue is that toolbars should only be navicable via arrow keys; tab key should take you out of the toolbar to the next (or previous is you use shift+tab) control.

VS Code version: Code - Insiders 1.34.0-insider (0ab39f4, 2019-04-08T05:19:58.162Z)
OS version: Windows_NT x64 10.0.17134

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz (4 x 3192)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: unavailable_off surface_synchronization: enabled_on video_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.93GB (11.19GB free)
Process Argv
Screen Reader	yes
VM	0%

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