Update build.mill

Author: lihaoyi

example/scalalib/basic/1-simple/build.mill

@@ -25,7 +25,8 @@ object `package` extends RootModule with ScalaModule {
 //// SNIPPET:END
 //
 // You can download this example project using the *download* link above
-// if you want to try out the commands below yourself. The only requirement is
+// if you want to try out the commands below yourself, or browse the full sources
+// of the example (including supporting files) via the *browse* link. The only requirement is
 // that you have some version of the JVM installed; the `./mill` script takes
 // care of any further dependencies that need to be downloaded. All examples
 // in this documentation site are executable and are continually exercised as