about: link to and from the about page

The about page was not linked, added footer section on the settings
view to link to the about page. Also added a link from the about
page to link back to index.html.

src/about.html

@@ -19,6 +19,7 @@
         for more information about nostr protocol, check out
         <a href="https://nostr.info/" target="_blank" rel="noopener noreferrer">nostr.info</a>.
       </p>
+      back to <a href="/">nostr.ch</a>
     </main>
   </body>
 </html>

src/index.html

@@ -76,6 +76,11 @@
               <button type="button" name="import" tabindex="0" disabled>save</button>
             </div>
           </form>
+          <footer class="text">
+            <p>
+              <a href="/about.html">about nostr.ch</a>
+            </p>
+          </footer>
         </div>
       </div>
     </main>

src/main.css

@@ -88,8 +88,8 @@ img {
   max-width: 100%;
 }
 
-main.text {
-  margin: 2rem;
+.text {
+  margin: var(--gap);
 }
 
 .danger {