help: Document option to paste URL to create a named link.

- Adds a "Via paste" tab to document the new functionality.

Fixes #26892.

help/insert-a-link.md

@@ -10,6 +10,19 @@
 
 {start_tabs}
 
+{tab|via-paste}
+
+{!start-composing.md!}
+
+1. Select the text you want to linkify.
+
+1. Paste a URL to turn the selected text into a named link.
+
+!!! keyboard_tip ""
+
+    You can also use <kbd>Ctrl</kbd> + <kbd>Shift</kbd> + <kbd>L</kbd>
+    to insert link formatting.
+
 {tab|via-markdown}
 
 {!start-composing.md!}

zerver/lib/markdown/tabbed_sections.py

@@ -98,6 +98,7 @@ TAB_SECTION_LABELS = {
     "user": "User",
     "bot": "Bot",
     "on-sign-up": "On sign-up",
+    "via-paste": "Via paste",
     "via-markdown": "Via Markdown",
     "via-compose-box-buttons": "Via compose box buttons",
     "stream-compose": "Compose to a stream",