Use the polyfills version only
Use str_replace() instead of preg_replace()

At least for simple replacements. It performs better and works just as
well.
Updated README with more links
Add missing `break`
Add some styles needed when no `display: flex`
Try main:after {clear: both}
Button background fallbacks for no gradients
dialog is `display: none` until `[open]`

Necessary because `:not([open])` isn't always supported.
Hide <dialog> if `no-js`
Added new elements and changed order of others.
New function wordCount()

Returns the number of words (separated by spaces) in an element.
Commented out link to #comments
Added style for <figure>, <figcaption>, & nested <ol>s