Add support for italic rendering

[flybayer]

This adds support for italic rendering.

You can test it with this command:

echo -e '\x1B[3m italic \x1B[m off'

Let me know if you'd like any changes or anything else!

Related to #580

[Tyriar]

This is what I see when using Hack under Ubuntu (I have Hack Italic installed):

[Tyriar]

I think the problem is the ordering when using normal as the weight before setting .font to this:

normal italic 22.5px courier-new, courier, monospace

Results in the fallback:

10px sans-serif

I'll look into fixing this.

[Tyriar]

Should be fixed now, just needed to rearrange the font attributes.

[Tyriar]

@bgw FYI I'll merge this in, conflicts should be minimal in your PR

[ceoshikhar]

Still the italics aren't rendering for me. Any solution?

[Tyriar]

Works for me:

Guessing it's your font config.

[shivapoudel]

@Tyriar Help is appreciated for this Cascadia Code ticket microsoft/cascadia-code#515