Add invite dialog style

Author: weeman1337

res/css/views/dialogs/_InviteDialog.pcss

@@ -452,3 +452,8 @@ limitations under the License.
 .mx_InviteDialog_identityServer {
     margin-top: 1em; /* TODO: Use a spacing variable */
 }
+
+.mx_InviteDialog_oneThreepid {
+    font-size: $font-12px;
+    margin: $spacing-8 0;
+}

src/components/views/dialogs/InviteDialog.tsx

@@ -1362,7 +1362,11 @@ export default class InviteDialog extends React.PureComponent<Props, IInviteDial
         let onlyOneThreepidNote: React.ReactNode | null = null;
 
         if (!this.canInviteMore() || (this.hasFilterAtLeastOneEmail() && !this.canInviteThirdParty())) {
-            onlyOneThreepidNote = <div>{_t("Invites by email can only be sent one at a time")}</div>;
+            onlyOneThreepidNote = (
+                <div className="mx_InviteDialog_oneThreepid">
+                    {_t("Invites by email can only be sent one at a time")}
+                </div>
+            );
         } else {
             results = (
                 <div className="mx_InviteDialog_userSections">