Ease up diff backgrounds

[Slotos]

Lower the blend intensity to leave sufficient colour difference for the eye to catch on.

This changes

To

Red, grey, and green highlights are now readable on diff backgrounds, whereas before some text could become illegible.

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Light variant is improved as well:

Before:

After:

[mvllow]

Thanks for the PR! Happy to accept these changes as-is because it's quite the improvement, but curious if setting all the opacities to 0.2 looks good too? Just for consistency reasons.

[Slotos]

IIRC 0.3 was my initial adjustment, and dropping to 0.2 made a sizeable difference for green background, especially green-on-green cases. Red worked ok and I just lazed out of adjusting it further.

I've force pushed an update. Comparison screenshots follow:

DiffDelete 0.3 blend:

DiffDelete 0.2 blend:

[mvllow]

Thanks again :) Really appreciate the before/after screenshots – makes my life much easier!