chore: UMD demo update

Author: rstoenescu

dev-umd/index.mat.umd.html

@@ -38,7 +38,7 @@
             </q-item>
             <q-item @click.native="launch('https://discord.gg/5TDhbDg')">
               <q-item-side icon="chat"></q-item-side>
-              <q-item-main label="Discord Channel" sublabel="Quasar Community"></q-item-main>
+              <q-item-main label="Discord Chat Channel" sublabel="https://discord.gg/5TDhbDg"></q-item-main>
             </q-item>
             <q-item @click.native="launch('https://twitter.com/quasarframework')">
               <q-item-side icon="rss feed"></q-item-side>