Fix documentation for subsitution

examples/substitutions/README.md

diff --git a/examples/substitutions/README.md b/examples/substitutions/README.md
index 719c415..77cf481 100644
--- a/examples/substitutions/README.md
+++ b/examples/substitutions/README.md
@@ -138,7 +138,7 @@
     ]),
     project_brief = "$(DESCRIPTION)", # => "no stamp" or "//substitutions:build_description" if the build is stamped
     project_name = "$(NAME)", # => "substitutions"
-    doxyfile = ":doxyfile_template",
+    doxyfile_template = ":doxyfile_template",
     toolchains = [":make_var_substitution"],
 )
 ```