Add links to sponsor sites and show as list

README.md

@@ -153,7 +153,25 @@ We accept donations via [Patreon](https://www.patreon.com/jcbrand) and [Liberapa
 
 ## Sponsors
 
-* ![Blokt Crypto & Privacy](https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/blokt.png)
-* ![Codefirst](https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/codefirst.png)
-* ![KeyCDN](https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/keycdn.png)
-* ![Mailbox](https://raw.githubusercontent.com/conversejs/converse.js/master/logo/mailbox.svg)
+<ul>
+<li>
+  <a href="https://blokt.com?utm_source=conversejs" target="_blank" rel="noopener">
+    <img alt="Blokt Crypto & Privacy" src="https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/blokt.png" width="200">
+  </a>
+</li>
+<li>
+  <a href="https://www.codefirst.co.uk?utm_source=conversejs" target="_blank" rel="noopener">
+    <img alt="Codefirst" src="https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/codefirst.png" width="200">
+  </a>
+</li>
+<li>
+  <a href="https://www.keycdn.com?utm_source=conversejs" target="_blank" rel="noopener">
+    <img alt="KeyCDN" src="https://raw.githubusercontent.com/conversejs/converse.js/541613d1fea8aef364af00180f60e959162e5e4b/logo/keycdn.png" width="200">
+  </a>
+</li>
+<li>
+  <a href="https://mailbox.org?utm_source=conversejs" target="_blank" rel="noopener">
+    <img alt="Mailbox - Email and cloud storage" src="https://raw.githubusercontent.com/conversejs/converse.js/master/logo/mailbox.svg" width="120">
+  </a>
+</li>
+</ul>