Fix missing alt on images and icons

[jordanmccullough]

Addresses the build failures of the script/cibuild.

[jordanmccullough]

@gjtorikian Working on addressing all errors (missing alts, inaccessible resources, etc.) per the build failure since the introduction of HTML-Proofer.

I took a look at this PR that fixed relative paths, but seems something isn't playing nice with the relative paths of the images in the situation shown below. I can validate by inspecting the code, the paths of resources, and the page that the image is not missing. However, HTML-Proofer disagrees.

Let me know if you have ideas on this situation.

./_site/resources/videos/index.html: internal image assets/git-fringes.jpg does not exist

[gjtorikian]

Ugh! Looks like the relative path magic is not set for images, only links. The short-term fixes are to just:

1. Prepend ./ to the paths.
2. Ignore it

Will definitely fix it in HTML::Proofer as soon as feasibly possible.

[afeld]

@gjtorikian Mind creating a placeholder issue, just so we can follow along?

[jordanmccullough]

Reverse merge to update branch with (temporarily) disabled HTML-Proofer. Bringing in fixes thus far to mainline.

[gjtorikian]

@jordanmccullough @aden A fix is in: gjtorikian/html-proofer#23

I'm working on speeding Proofer up as well. This repository has about 500 files, and builds are taking upwards of 10 minutes. Expect a 0.3.1 release 🔜 ish (within this year).

[jordanmccullough]

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