Add para about registration to covid banner

Also change `/at-home` to `/learn` and open that link in a new window.

Author: patch0

src/common/cd-covid-banner.vue

@@ -3,7 +3,10 @@
       <p>{{ $t('Thank you for your interest in joining the CoderDojo community!') }}</p>
       <p>{{ $t('Due to the coronavirus pandemic, we have paused the Dojo verification process.') }}</p>
       <p>{{ $t('In the meantime, we’re providing exciting opportunities for young people, parents, volunteers, and educators to get creative with tech through') }}
-        <a class="cd-banner-link" href="https://www.raspberrypi.org/at-home/?utm_source=coderdojo&utm_medium=covid-banner&utm_campaign=dmah">{{ $t('Digital Making at Home') }}</a> {{ $t('from the Raspberry Pi Foundation.') }}
+        <a class="cd-banner-link" target="_blank" href="https://www.raspberrypi.org/learn/?utm_source=coderdojo&utm_medium=covid-banner&utm_campaign=dmah">{{ $t('Digital Making at Home') }}</a> {{ $t('from the Raspberry Pi Foundation.') }}
+      </p>
+      <p>{{ $t('There are still many ways for you to get involved in the Raspberry Pi community!') }}
+        <a class="cd-banner-link" href="https://zen.coderdojo.com/dashboard/start-dojo">{{ $t('Please register your details') }}</a> {{ $t('with us so we can find out how best to support you.') }}
       </p>
     </div>
 </template>