Docs: Broken link in usage instructions

[coliff]

Near the bottom of the page at: https://icons.getbootstrap.com/#working-with-svgs there is a link to https://simplyaccessible.com/article/7-solutions-svgs/#acc-heading-2 which is dead. The domain isn't accessible so I think the link should be removed.

Seeing as that link doesn't work and the other two links are regarding Internet Explorer perhaps this whole section could be removed?

Alternatively, link to:
https://web.archive.org/web/20201112013541/https://simplyaccessible.com/article/7-solutions-svgs/#acc-heading-2
or perhaps this article:
https://www.scottohara.me/blog/2019/05/22/contextual-images-svgs-and-a11y.html

[XhmikosR]

Feel free to make a PR with the web archive link for now.