asciidoctor-with-extensions: add Java dependency

The asciidoctor-diagram extension vendors JARs and requires a JRE to
render ditaa and PlantUML diagrams.

Resolves:

    $ asciidoctor --require asciidoctor-diagram - >/dev/null <<ADOC
    [ditaa]
    ....
    +---+   +---+
    | A +-->| B |
    +---+   +---+
    ....
    ADOC
    asciidoctor: ERROR: <stdin>: line 2: Failed to generate image: Could not find Java executable

pkgs/tools/typesetting/asciidoctor-with-extensions/default.nix

@@ -2,9 +2,13 @@
 , bundlerApp
 , bundlerUpdateScript
 , makeWrapper
+, withJava ? true, jre # Used by asciidoctor-diagram for ditaa and PlantUML
 }:
 
-bundlerApp {
+let
+  path = lib.makeBinPath (lib.optional withJava jre);
+in
+bundlerApp rec {
   pname = "asciidoctor";
   gemdir = ./.;
 
@@ -16,6 +20,13 @@ bundlerApp {
     "asciidoctor-revealjs"
   ];
 
+  buildInputs = [ makeWrapper ];
+
+  postBuild = lib.optionalString (path != "") (lib.concatMapStrings (exe: ''
+    wrapProgram $out/bin/${exe} \
+      --prefix PATH : ${path}
+  '') exes);
+
   passthru = {
     updateScript = bundlerUpdateScript "asciidoctor-with-extensions";
   };