doc: move image builders into new images chapter

doc/builders/images.xml

@@ -0,0 +1,12 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-images">
+ <title>Images</title>
+ <para>
+  This chapter describes tools for creating various types of images.
+ </para>
+ <xi:include href="images/appimagetools.xml" />
+ <xi:include href="images/dockertools.xml" />
+ <xi:include href="images/ocitools.xml" />
+ <xi:include href="images/snaptools.xml" />
+</chapter>

doc/functions.xml

@@ -12,10 +12,6 @@
  <xi:include href="functions/debug.xml" />
  <xi:include href="functions/fhs-environments.xml" />
  <xi:include href="functions/shell.xml" />
- <xi:include href="functions/dockertools.xml" />
- <xi:include href="functions/snaptools.xml" />
- <xi:include href="functions/appimagetools.xml" />
  <xi:include href="functions/prefer-remote-fetch.xml" />
  <xi:include href="functions/nix-gitignore.xml" />
- <xi:include href="functions/ocitools.xml" />
 </chapter>

doc/manual.xml

@@ -24,6 +24,7 @@
   <title>Builders</title>
   <xi:include href="builders/fetchers.xml" />
   <xi:include href="builders/trivial-builders.xml" />
+  <xi:include href="builders/images.xml" />
   <xi:include href="languages-frameworks/index.xml" />
   <xi:include href="packages/index.xml" />
  </part>