Add support more favicon types (-favicon mmh3 probe enchant)

[vypivshiy]

httpx version:

v1.6.6

Current Behavior:

Some sites do not adhere to the standard of using .ico format in the html tag <link rel="shortcut icon"...>.
It can be contain svg, png, jpg, jpeg, gif and less often base64 encoded string 🤯

Currently this project only supports .ico for this probe method.

Expected Behavior:

Add more formats support for probe favicon's. sometimes it doesn't find

Steps To Reproduce:

I collect several examples of sites in the wild for testing for next format:

1. command for reproduce
2. html icon tags in examples pages

• 1 not founded favicon.ico

httpx -u https://0-cenka.ru -silent -favicon -fhr
https://0-cenka.ru []

<link rel="apple-touch-icon" href="apple-touch-icon.png">		
<link rel="shortcut icon" href="favicon.ico">

• 2 not founded favicon.ico + another types

httpx -u https://0360.ru -silent -favicon -fhr
https://0360.ru []

<link rel="icon" type="image/x-icon" href="favicon.ico">
<link rel="apple-touch-icon" href="favicon_180x180.png">
<link rel="icon" href="favicon.svg">

• 3 png format only in rel-icon tags

httpx -u https://viber.com -silent -favicon -fhr
https://viber.com []

<link rel="shortcut icon" href="https://www.viber.com/app/themes/viber/assets/images/favicon.png" type="image/vnd.microsoft.icon"/>

• 4 emoji as favicon (original site favicon contains)

httpx -u https://favicon.io/emoji-favicons/alien/  -silent -favicon
https://favicon.io/emoji-favicons/alien/ []

<link data-vue-tag="ssr" rel="icon" href="data:,">
    <link data-vue-tag="ssr" rel="icon" type="image/png" sizes="96x96"
          href="/assets/static/favicon.b9532cc.ed88c65f76fa003989a0c683d668c765.png">

• 5 ultra rare base64 encoded icon

httpx -u https://00j.ru/ -silent -favicon -fhr
https://00j.ru/ []

<link rel="icon" type="image/gif" href="data:image/gif;base64,...">

Anything else:

Other refs that might help:

• x.com tweet 2020 - svg emoji as favicon
• developer.mozilla.org - mozilla rel-icon doc
• html.spec.whatwg.org - html5 rel-icon specs
• mathiasbynens.be (rel="shortcut icon" considered harmful) - post from 2010, IE browser before 11v does not support rel='shortcut icon' attr and formats other than .ico. I added this link just for fun