Add modular style B2 project file. (#11)

* Add modular build support.
* Tweak example to use the modular target.

Author: grafikrobot

README.md

@@ -6,14 +6,9 @@ befitting the quality of Boost.
 
 Example of integration into a doc Jamfile:
 ```
-path-constant boostlook : ../../../tools/boostlook ;
-
 html mp11.html : mp11.adoc
-    : <asciidoctor-attribute>stylesheet=$(boostlook)/boostlook.css
-      <flags>"-r $(boostlook)/boostlook.rb"
-      <dependency>$(boostlook)/boostlook.css
-      <dependency>$(boostlook)/boostlook.rb
-      <dependency>mp11-docinfo-footer.html
+    :   <use>/boost/boostlook//boostlook
+        <dependency>mp11-docinfo-footer.html
     ;
 ```
 

build.jam

@@ -0,0 +1,22 @@
+# Copyright René Ferdinand Rivera Morell 2024
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+
+require-b2 5.2 ;
+
+project /boost/boostlook ;
+
+path-constant here : . ;
+
+alias boostlook
+    : usage-requirements
+        <asciidoctor-attribute>stylesheet=$(here)/boostlook.css
+        <flags>"-r $(here)/boostlook.rb"
+        <dependency>boostlook.css
+        <dependency>boostlook.rb
+    ;
+explicit boostlook ;
+
+alias all ;
+explicit all ;