accounts: share telegram linking modal with other pages

the one on the admin page was a little messed up anyway. Not relevant to
the other linking modals, as the process is different (simpler) on the
admin page.

html/account-linking-discord.html

@@ -0,0 +1,16 @@
+{{ if .discordEnabled }}
+<div id="modal-discord" class="modal">
+    <div class="card relative mx-auto my-[10%] w-4/5 lg:w-1/3">
+        <span class="heading mb-4">{{ .strings.linkDiscord }}</span>
+        <p class="content mb-4"> {{ .discordSendPINMessage }}</p>
+        <h1 class="text-center text-2xl mb-2 pin"></h1>
+        <div class="row center">
+            <a class="my-5 hover:underline">
+                <span class="mr-2">{{ .strings.joinTheServer }}</span>
+                <span id="discord-invite"></span>
+            </a>
+        </div>
+        <span class="button ~info @low full-width center mt-4" id="discord-waiting">{{ .strings.success }}</span>
+    </div>
+</div>
+{{ end }}