fix some accessibilty issues

_includes/footer.njk

@@ -1,7 +1,7 @@
 <footer>
   <ul>
     <li>
-      <a href="/colophon" title="colophon"
+      <a href="/colophon/"
       {% if page.url == "/colophon/" %}aria-current="page"{% endif %}>
         colophon
       </a>

_includes/header.njk

@@ -1,6 +1,6 @@
 <header>
 
-  <a href="#main" id="skip" title="skip to main content" aria-label="skip to main content">
+  <a href="#main" id="skip" title="skip to main content">
     <i class="fa-solid fa-forward" aria-hidden="true"></i> skip
   </a>