Render favicon in admin area the same way as on frontend

[Jimmi08]

Motivation

one rule for favicon rendering correct site favicon visible in admin asap after loading in prefs

Proposed Solution

renderFavicon() to admin header.php

Additional Context

It is easy to change. But the function renderFavicon() is part of header_default.php so it would be needed to copy to admin/header.php. And it means duplicate code for the same thing.

Thanks

// --------  Generate Apple Touch Icon ---------
echo renderFavicon();

function renderFavicon()
{
    // ---------- Favicon ---------
    if (file_exists(THEME . "favicon.ico"))
    {
        return "<link rel='icon' href='" . THEME_ABS . "favicon.ico' type='image/x-icon' />\n<link rel='shortcut icon' href='" . THEME_ABS . "favicon.ico' type='image/xicon' />\n";
    }
    elseif (file_exists(e_MEDIA_ICON . '16x16_favicon.png'))
    {
        $iconSizes = [16 => 'icon', 32 => 'icon', 48 => 'icon', 192 => 'icon', 167 => 'apple-touch-icon', 180 => 'apple-touch-icon'];
        $text = '';
        foreach ($iconSizes as $size => $rel)
        {
            $sizes = $size . 'x' . $size;
            $text .= "<link rel='$rel' type='image/png' sizes='$sizes' href='" . e_MEDIA_ICON_ABS . $sizes . "_favicon.png'>\n";
        }
        return $text;
    }
    elseif (file_exists(e_BASE . "favicon.ico"))
    {
        return "<link rel='icon' href='" . SITEURL . "favicon.ico' type='image/x-icon' />\n<link rel='shortcut icon' href='" . SITEURL . "favicon.ico' type='image/xicon' />\n";
    }
}

[CaMer0n]

@Jimmi08 This has been completed. Please comment here if you find any issues with the commit.