docs(usage): option name is implementation-defined

fix #828

Author: alandefreitas

docs/modules/ROOT/pages/config-file.adoc

@@ -149,13 +149,13 @@ namespace my_library
 
 === Private Symbols
 
-The `implementation-detail` and `see-below` options can be used to designate symbols as implementation details or "see below" in the documentation.
+The `implementation-defined` and `see-below` options can be used to designate symbols as implementation details or "see below" in the documentation.
 
 [,yaml]
 ----
 include-symbols:
   - 'my_library::**'
-implementation-detail:
+implementation-defined:
   - 'my_library::detail::**'
 see-below:
   - 'my_library::see_below::**'

docs/modules/ROOT/pages/usage.adoc

@@ -233,7 +233,7 @@ And the user can specify that symbols in the `impl` namespace are implementation
 [source,yaml]
 ----
 # ...
-implementation-detail: impl::**
+implementation-defined: impl::**
 # ...
 ----