doc: move section darwin-builder under chapter packages

Changed files
+1 -1
doc
-1
doc/builders/special.md
···
special/fhs-environments.section.md
special/makesetuphook.section.md
special/mkshell.section.md
-
special/darwin-builder.section.md
special/vm-tools.section.md
```
doc/builders/special/darwin-builder.section.md doc/packages/darwin-builder.section.md
+1
doc/packages/index.md
···
```{=include=} sections
citrix.section.md
+
darwin-builder.section.md
dlib.section.md
eclipse.section.md
elm.section.md