Verify favicon metadata is correct

[JasonYao]

• Make a favicon image srcset, or update for the favicons I created 4 years ago, since current code is:

  <link rel="shortcut icon" href="{{ .Site.Params.favicon | absURL }}favicon.ico" type="image/x-icon">
  <link rel="apple-touch-icon" sizes="180x180" href="{{ .Site.Params.favicon | absURL }}apple-touch-icon.png">
  <link rel="icon" type="image/png" sizes="32x32" href="{{ .Site.Params.favicon | absURL }}favicon-32x32.png">
  <link rel="icon" type="image/png" sizes="16x16" href="{{ .Site.Params.favicon | absURL }}favicon-16x16.png">

Old code for favicons:

<link rel="apple-touch-icon" sizes="180x180" href="/assets/img/favicons/apple-touch-icon.png">
<link rel="icon" type="image/png" sizes="32x32" href="/assets/img/favicons/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/assets/img/favicons/favicon-16x16.png">
<link rel="manifest" href="/manifest.json">
<link rel="mask-icon" href="/assets/img/favicons/safari-pinned-tab.svg" color="#5bbad5">
<link rel="shortcut icon" href="/assets/img/favicons/favicon.ico">
<meta name="msapplication-config" content="/assets/img/favicons/browserconfig.xml">
<meta name="theme-color" content="#ffffff">

from https://github.com/JasonYao/deprecated-old-2017-site/blob/source/_includes/head.html#L40-L47

[JasonYao]

Per https://evilmartians.com/chronicles/how-to-favicon-in-2021-six-files-that-fit-most-needs, this looks to be the simplified approach nowadays:

HTML in header

<link rel="icon" href="/favicon.ico"><!-- 32×32 -->
<link rel="icon" href="/icon.svg" type="image/svg+xml">
<link rel="apple-touch-icon" href="/apple-touch-icon.png"><!-- 180×180 -->
<link rel="manifest" href="/manifest.webmanifest">

Favicon manifest file

{
  "icons": [
    { "src": "/192.png", "type": "image/png", "sizes": "192x192" },
    { "src": "/512.png", "type": "image/png", "sizes": "512x512" }
  ]
}