help: Add a dedicated page on how to format links.

Also remove the Images section from the "Message formatting" help
page, and drop unused markdown-image.png.

Fixes part of #24209.

help/format-your-message-using-markdown.md

@@ -16,7 +16,7 @@ whenever you need a reminder of the formatting syntax below.
 * [Text emphasis](#text-emphasis)
 * [Bulleted lists](#bulleted-lists)
 * [Numbered lists](#numbered-lists)
-* [Links and images](#links)
+* [Links](#links)
 * [Code blocks](#code)
 * [LaTeX](#latex)
 * [Quotes](#quotes)
@@ -42,32 +42,14 @@ whenever you need a reminder of the formatting syntax below.
 
 ## Links
 
-Zulip auto-linkifies URLs and [valid stream (and topic) names][link-to-conversation].
+{!links-intro.md!}
-You can also add a [custom linkifier](/help/add-a-custom-linkifier) to link
-patterns like `#1234` to your ticketing system.
 
-[link-to-conversation]: /help/link-to-a-message-or-conversation
+{!links-examples.md!}
 
-```
+!!! tip ""
-Auto-detected URL: zulip.com
+    You can also use a button or a keyboard shortcut (<kbd>Ctrl</kbd> +
-Named link: [Zulip homepage](zulip.com)
+    <kbd>Shift</kbd> + <kbd>L</kbd>) to insert a link.
-Stream: #**stream name**
+    [Learn more](/help/insert-a-link).
-Topic: #**stream name>topic name**
-Custom linkifier: #1234 (links to ticket 1234 in your ticketing system)
-```
-
-![Markdown links](/static/images/help/markdown-links.png)
-
-## Images
-
-See [Share and upload files](/help/share-and-upload-files) to learn more
-about dropping, pasting, and attaching images.
-
-```
-[A whale of a good time](https://your.zulip.domain/user_uploads/1/46/IPvysqXEtiTG1ZdNBrwAZODi/whale-time.png)
-```
-
-![Markdown image](/static/images/help/markdown-image.png)
 
 ## Code
 

help/include/links-examples.md

@@ -0,0 +1,13 @@
+### What you type
+
+```
+Named link: [Zulip homepage](zulip.com)
+A URL (links automatically): zulip.com
+Stream link: #**stream name**
+Stream and topic link: #**stream name>topic name**
+Custom linkifier: For example, #2468 can automatically link to an issue in your tracker.
+```
+
+### What it looks like
+
+![Markdown links](/static/images/help/markdown-links.png)

help/include/links-intro.md

@@ -0,0 +1,8 @@
+In Zulip, you can insert a named link using Markdown formatting. In addition, Zulip
+automatically creates links for you when you enter:
+
+- A URL
+- An appropriately formatted stream name, or a stream name followed by a topic
+  (see also [Link to a message or
+  conversation](/help/link-to-a-message-or-conversation))
+- Text that matches a [custom linkifier](/help/add-a-custom-linkifier) set up by your organization

help/include/sidebar_index.md

@@ -60,6 +60,7 @@
 * [Mention a user or group](/help/mention-a-user-or-group)
 * [Quote and reply](/help/quote-and-reply)
 * [Emoji and emoticons](/help/emoji-and-emoticons)
+* [Insert a link](/help/insert-a-link)
 * [Share and upload files](/help/share-and-upload-files)
 * [Add GIFs in your message](/help/animated-gifs-from-giphy)
 * [Text emphasis](/help/text-emphasis)

help/insert-a-link.md

@@ -0,0 +1,50 @@
+# Insert a link
+
+{!links-intro.md!}
+
+## Examples
+
+{!links-examples.md!}
+
+## Insert a link
+
+{start_tabs}
+
+{tab|via-markdown}
+
+{!start-composing.md!}
+
+1. Wrap the link text in square brackets followed by the URL
+   wrapped in parentheses to create a named link:  
+   `[link text](URL)`
+
+!!! keyboard_tip ""
+
+    You can also use <kbd>Ctrl</kbd> + <kbd>Shift</kbd> + <kbd>L</kbd>
+    to insert link formatting.
+
+{tab|via-compose-box-buttons}
+
+{!start-composing.md!}
+
+1. Select the text you want to linkify.
+
+1. Click the **link** (<i class="fa fa-link"></i>) icon at the
+   bottom of the compose box.
+
+1. Replace `url` with a valid URL.
+
+!!! keyboard_tip ""
+
+    You can also use <kbd>Ctrl</kbd> + <kbd>Shift</kbd> + <kbd>L</kbd>
+    to insert link formatting.
+
+{end_tabs}
+
+## Related articles
+
+* [Message formatting](/help/format-your-message-using-markdown)
+* [Preview messages before sending](/help/preview-your-message-before-sending)
+* [Resize the compose box](/help/resize-the-compose-box)
+* [Animated GIFs](/help/animated-gifs-from-giphy)
+* [Video calls](/help/start-a-call)