High Contrast support

[joaomoreno]

Issue: #2711 #3184
Assignees:

• Windows @alexandrudima
• OS X @isidorn
• Linux @joaomoreno

Details:

• For each platform, can you enable the "High Contrast" theme?
• Select some chunks of code. Is any part of the selection illegible (e.g. light text on the white selection overlay)?
• Click on a variable in your code. Verify word matching is visible.
• Use "Find" to find something. Verify word matching is visible.
• Toggle on/off each viewlet from the activity bar. Do any icons disappear or look weird?

[joaomoreno]

@bgashler1 Don't forget to add details of this test plan item, for us to test tomorrow.

[bgashler1]

Thanks @joaomoreno. Will do this right now.