new site param: logoAlt

exampleSite/config.yaml

@@ -28,6 +28,7 @@ params:
   search: true
   showThemeSwitcher: true
   moveFooterToHeader: false
+  logoAlt: "An alternative text description of the logo"
   customCss:
     - css/custom_01.css
     - css/custom_02.css

layouts/partials/header.html

@@ -6,7 +6,9 @@
         href="{{ .Site.BaseURL }}"
         aria-label="{{ .Site.Title }} home page"
       >
-        <img src="{{ "images/logo.svg" | relURL }}" alt="">
+        <img 
+          src="{{ "images/logo.svg" | relURL }}" 
+          alt="{{ .Site.Params.logoAlt | default "Logo" }}">
       </a>
       <p class="library-desc">
         {{ with .Site.Params.description }} {{ . | markdownify }} {{ end }}