Add /download/4.x redirects for the current download page

This also adjusts the format for redirects to make sure
pages are always generated as `/index.html`.
This happens when the redirect link ends with a slash, no
explicit declaration needed. So I adjusted existing rules
to use that as well.

_config.yml

@@ -25,7 +25,7 @@ collections:
     output: true
   download_3:
     output: true
-    permalink: /download/3.x/:name/index.html
+    permalink: /download/3.x/:name/
 
 # Build collection items with a future date.
 future: true

collections/_download/android.md

@@ -16,6 +16,9 @@ downloads:
 ignore_export: true
 ignore_mono: true
 
+redirect_from:
+  - /download/4.x/android/
+
 content_note: |
   <p>
     <strong>Note:</strong> C# support is not available in the Android editor.

collections/_download/linux.md

@@ -17,6 +17,9 @@ downloads:
   - platform: "linux.32"
     mono: true
 
+redirect_from:
+  - /download/4.x/linux/
+
 content_instructions: |
   <ul>
     <li>Extract and run. Godot is self-contained and does not require installation.</li>

collections/_download/macos.md

@@ -13,7 +13,8 @@ downloads:
     featured_flavor: .NET
 
 redirect_from:
-  - /download/osx
+  - /download/4.x/macos/
+  - /download/osx/
 
 content_instructions: |
   <ul>

collections/_download/windows.md

@@ -19,6 +19,9 @@ downloads:
   - platform:  "windows.32"
     mono: true
 
+redirect_from:
+  - /download/4.x/windows/
+
 content_note: |
   <p>
     <strong>Note:</strong> The 32-bit .NET binaries do not run on 64-bit Windows systems at the time being. Make sure to export 64-bit .NET binaries for your 64-bit target platforms.

collections/_download_3/server.md

@@ -18,7 +18,7 @@ downloads:
     mono: true
 
 redirect_from:
-  - /download/server
+  - /download/server/
 
 content_instructions: |
   <ul>

pages/blog/blog.html

@@ -7,8 +7,9 @@ pagination:
   enabled: true
   collection: article
 redirect_from:
-  - /devblog/index.html
-  - /news/index.html
-  - /news/default/1/index.html
-  - /news/default/2/index.html
+  - /devblog/
+  - /news/
+  - /news/default/
+  - /news/default/1/
+  - /news/default/2/
 ---

pages/contact.html

@@ -6,7 +6,7 @@ layout: more
 header_text: "Contact us"
 current_tab: "contact"
 redirect_from:
-  - /more/index.html
+  - /more/
 ---
 
 <div class="container-text">

pages/download.html

@@ -3,6 +3,9 @@ permalink: /download/index.html
 title: "Download - Godot Engine"
 description: "Download the latest stable version of the Godot Engine for Linux, macOS, Windows, or Android"
 layout: default
+
+redirect_from:
+  - /download/4.x/
 ---
 
 <div style="padding: 16px 32px">