docs: add slack username helptext (#5259)

Co-authored-by: Frank Elsinga <frank@elsinga.de>

src/components/notifications/Slack.vue

@@ -4,6 +4,9 @@
         <input id="slack-webhook-url" v-model="$parent.notification.slackwebhookURL" type="text" class="form-control" required>
         <label for="slack-username" class="form-label">{{ $t("Username") }}</label>
         <input id="slack-username" v-model="$parent.notification.slackusername" type="text" class="form-control">
+        <div class="form-text">
+            {{ $t("aboutSlackUsername") }}
+        </div>
         <label for="slack-iconemo" class="form-label">{{ $t("Icon Emoji") }}</label>
         <input id="slack-iconemo" v-model="$parent.notification.slackiconemo" type="text" class="form-control">
         <label for="slack-channel" class="form-label">{{ $t("Channel Name") }}</label>

src/lang/en.json

@@ -721,6 +721,7 @@
     "Icon Emoji": "Icon Emoji",
     "signalImportant": "IMPORTANT: You cannot mix groups and numbers in recipients!",
     "aboutWebhooks": "More info about Webhooks on: {0}",
+    "aboutSlackUsername": "Changes the display name of the message sender. If you want to mention someone, include it in the friendly name instead.",
     "aboutChannelName": "Enter the channel name on {0} Channel Name field if you want to bypass the Webhook channel. Ex: #other-channel",
     "aboutKumaURL": "If you leave the Uptime Kuma URL field blank, it will default to the Project GitHub page.",
     "smtpDkimSettings": "DKIM Settings",