Fix links

Author: mattcone

Rakefile

@@ -19,6 +19,7 @@ task :test do
                     %r{https://hedgedoc.org/*},
                     %r{https://docs.hedgedoc.org/*},
                     %r{https://www.reddit.com/*}],
+                    %r{https://stackoverflow.com/*}],
     :url_swap => { %r{https://www.markdownguide.org} => '' },
     :typhoeus => {
       :ssl_verifypeer => false,

_tools/airsend.md

@@ -63,9 +63,6 @@ syntax:
     available: n
   - id: html
     available: n
-see-also:
-  - name: AirSend Markdown Cheatsheet
-    link: https://www.airsend.io/blog/index.php/2020/02/19/how-to-format-a-message-using-markdown-language/
 ---
 
 [AirSend](https://www.airsend.io/) is a collaboration application that's great for keeping track of notes, formatting documents, and publishing status reports. This application allows users to see their notes and status reports in Markdown-formatted text. While typing your notes, other users can see the live preview on their screens. AirSend is available for macOS, iOS, Android, Windows, and Linux.

_tools/codimd.md

@@ -62,8 +62,8 @@ syntax:
   - id: html
     available: y
 see-also:
-  - name: CodiMD features
-    link: https://codimd-app.herokuapp.com/features
+  - name: CodiMD documentation
+    link: https://hackmd.io/c/codimd-documentation/
 ---
 
 [CodiMD](https://github.com/hackmdio/codimd) is an open-source real-time collaborative Markdown editor. You can easily [deploy CodiMD with Docker following this tutorial](https://hackmd.io/s/codimd-docker-deployment). CodiMD supports CommonMark and other markup syntax, such as:

tools.md

@@ -2,7 +2,7 @@
 layout: tools
 title: Tools
 description: Applications and components that support Markdown.
-last_modified_at: 2024-10-01
+last_modified_at: 2025-06-19
 ---
 
 <div class="row">