Adjust `editor.selectionBackground` & `editor.selectionHighlightBackground`

[wenfangdu]

Currently, these two colors are almost indistinguishable, more contrast would be better.

Can't tell statusBar with the cursor is selected or not:

[dsifford]

I tried playing with this for a bit just now and it's unfortunately not as simple as just adjusting those two regions.

This gets tricky, particular in "smarter" synataxes (like javascript, for example) because editor.wordHighlightBackground and editor.wordHighlightStrongBackground seem to also play a role in this and that role appears to be of a higher priority.

So I'm not sure there is an easy fix. Feel free to propose a solution if you have one.

[wenfangdu]

@dsifford Fixing #184 would partially solve this issue.

As for

This gets tricky, particularly in "smarter" syntaxes (like javascript, for example) because editor.wordHighlightBackground and editor.wordHighlightStrongBackground seem to also play a role in this and that role appears to be of a higher priority.

We can fix this later if a better solution is raised.

[wenfangdu]

@dsifford @luxonauta @zenorocha Please reopen this issue, since #253 has been reverted.