SVG void elements don't have a slash

[taronull]

Temple is amazing so far. Thanks for this library.

Describe the bug
SVG void elements nest siblings without a self-closing slash

To Reproduce
Steps to reproduce the behavior:

def test do
  temple do
    rect width: "256"
    circle cx: "128"
  end
end
# "<rect width=\"256\">\n<circle cx=\"128\">\n"

In browser, unintended closing tag is added

<!-- -->
<rect width="256">
  <circle cx="128">
</rect>

Expected behavior
A clear and concise description of what you expected to happen.

rect width: "256"
circle cx: "128"

Should result in

<!-- In browser, unintended closing tag is added -->
<rect width="256" />
<circle cx="128" />

Should equal

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: macOS Monterey 12.7.6
• Temple Version: 13
• Elixir Version: 1.17
• Erlang Version: 27

Additional context
Add any other context about the problem here.

Current workaround is /: true attribute.

I think Temple could add a slash to all self-closing tags because HTML has no problem with them.

[mhanberg]

It looks like I'm the html spec, all foreign elements (svg and math ml) have to be self closing, probably an easy fix here.