Remove alt attribute when inlining SVG images

[olajideoye]

Inlining an SVG image tag containing an alt attribute works as expected: it generates an <svg> element containing the alt attribute (since attributes are preserved). The only problem is that alt attributes aren't allowed in SVG elements and throws and throws an error when validated with the W3C HTML Validator.

So inlining something like this

<img src="github.svg" alt="GitHub" inline>

generates this (as expected)

<svg width="40" height="40" viewBox="0 0 40 40" alt="GitHub">...</svg>

but fails the W3C HTML Validator:

Please check here for a list of allowed attributes

[olajideoye]

I'll write a fix for this an create a pull request.