Support link underlines in the DOM renderer

[agurod42]

Closes #1704

[Tyriar]

I believe we should consider the border-bottom approach in this case. But of course, you've the last word 😊

I don't actually see that AA issue in Chrome 69, is that the browser you're using? I would prefer to use text-decoration as it simplified the logic a lot plus gives the nice perk of fancy underlines:

I removed box-sizing: border-box, are you still able to reproduce the AA problem on your mac?

[agurod42]

I was testing on vscode itself. But it also happens on my Chrome:

I noticed also, that if you zoom the image you posted just before the gaps are also there:

[agurod42]

Interesting fact: The AA problem disappears if the span width is a number without decimals (By default it computes to 7.234375px in my environment when using font-size 12).

[Tyriar]

Lol, it was there on mine, I didn't even notice. I suspect this issue isn't present on lower DPI screens and I say we go ahead with this as is as it's barely noticeable. Thoughts @agurodriguez?

Also, the character width has to be a decimal for the DOM renderer, this uses the width the font specifies.

[agurod42]

Yeahp, I do agree it's barely noticeable. Let's go ahead.