Migrate "reference" documents to HTML5

[ptziegler]

This change includes:

• Changing the doctype to "html".

• Simplifying the "Content-Type" meta element to only retain the encoding. The remaining attributes match the default settings and can be omitted.

• Removing the obsolete "charset attribute of the "link" element. The encoding is specified via the "Content-Type" header of the linked document.

• Removing the redundant "type" attribute for the "style" element. CSS is the default type and can therefore be omitted.

• Removing the obsolete "Content-Style-Type" meta element. Styles use CSS by default, so there is no need to set it globally for the document.

• Removing the obsolete "Content-Language" meta element. The document language is specified at the root element.

• Converting the obsolete "name" attribute of anchor points to "id" attributes of their nearest container and removing the "a" element all-together.

• Translating the styling of HTML elements to CSS.

• Cleanup of broken HTML or broken references.

[ptziegler]

I've checked the documents using the Nu HTML checker, which is the same validator used by e.g. #3238.

I've fixed all errors and warnings, outside of the deprecated <tt> element, because that would overshadow all other changes.

[akurtakov]

Thanks @ptziegler ! Much appreciated! Let's merge once 4.38 stream opens.

[eclipse-platform-bot]

This pull request changes some projects for the first time in this development cycle.
Therefore the following files need a version increment:

eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml

An additional commit containing all the necessary changes was pushed to the top of this PR's branch. To obtain these changes (for example if you want to push more changes) either fetch from your fork or apply the git patch.

Git patch

From 3664165f1f016b47fa61a20a21eb0241fea21c1d Mon Sep 17 00:00:00 2001
From: Eclipse Platform Bot <[email protected]>
Date: Mon, 1 Sep 2025 06:09:47 +0000
Subject: [PATCH] Version bump(s) for 4.38 stream


diff --git a/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml b/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
index bae7e9d0a5..18cc7250f9 100644
--- a/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
+++ b/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
@@ -3,7 +3,7 @@
 <feature
       id="org.eclipse.help"
       label="%featureName"
-      version="2.3.2300.qualifier"
+      version="2.3.2400.qualifier"
       provider-name="%providerName"
       plugin="org.eclipse.help.base"
       license-feature="org.eclipse.license"
-- 
2.51.0

Further information are available in Common Build Issues - Missing version increments.

[akurtakov]

Sorry for the noise! I misclicked and created a merge request and had to remove it after that.