I notice the cursor fg is unexpectedly blue sometimes, I would have thought this is black:

Underline and bar cursors don't seem to update correctly atm

Changing to light theme in demo still shows white block cursor:

Fixed the blue problem, was related to rgba format being used as rgb f64cb15

The light theme issue is actually a problem outside of this PR as the cursor colors don't get set in the theme so the defaults are used.

Just need to fix the tests:

  1) WebGL Renderer Integration Tests
       dispose removes renderer canvases:

      AssertionError: expected 2 to equal 3
      + expected - actual

      -2
      +3
      
      at Context.<anonymous> (addons\xterm-addon-webgl\test\WebglRenderer.api.ts:28:12)
      at Generator.next (<anonymous>)
      at fulfilled (addons\xterm-addon-webgl\out-test\WebglRenderer.api.js:5:58)