asciidoctor: add the tilt gem

This will enable the Asciidoctor's templating feature:

https://docs.asciidoctor.org/asciidoctor/latest/convert/templates/

The ERB templates will work out-of-the box, any other templates (such as Haml
or Slim) would need additional gems installed:

https://github.com/rtomayko/tilt#readme

Fixes: #104815

pkgs/tools/typesetting/asciidoctor/Gemfile

@@ -4,3 +4,4 @@ gem 'asciidoctor-pdf'
 gem 'coderay'
 gem 'pygments.rb'
 gem 'rouge'
+gem 'tilt'

pkgs/tools/typesetting/asciidoctor/Gemfile.lock

@@ -49,6 +49,8 @@ GEM
     rexml (3.2.5)
     rouge (4.0.0)
     ruby-rc4 (0.1.5)
+    temple (0.10.2)
+    thor (1.2.2)
     treetop (1.6.11)
       polyglot (~> 0.3)
     ttfunk (1.7.0)
@@ -64,4 +66,4 @@ DEPENDENCIES
   rouge
 
 BUNDLED WITH
-   2.3.22
+   2.4.13

pkgs/tools/typesetting/asciidoctor/gemset.nix

@@ -238,6 +238,26 @@
     };
     version = "0.1.5";
   };
+  temple = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "09p32vp94sa1mbr0if0adf02yzc4ns00lsmpwns2xbkncwpzrqm4";
+      type = "gem";
+    };
+    version = "0.10.2";
+  };
+  thor = {
+    groups = ["default"];
+    platforms = [];
+    source = {
+      remotes = ["https://rubygems.org"];
+      sha256 = "0k7j2wn14h1pl4smibasw0bp66kg626drxb59z7rzflch99cd4rg";
+      type = "gem";
+    };
+    version = "1.2.2";
+  };
   treetop = {
     dependencies = ["polyglot"];
     groups = ["default"];