[Doc] Add documentation top-level namespace App

src/App/ExpressionParser.h

@@ -594,6 +594,12 @@ protected:
     std::string end;
 };
 
+/**
+ * Namespace for parsing expressions.
+ *
+ * Contains functionality for parsing expressions, the units of
+ * expressions, whether a token is an identifier, unit, or constant.
+ */
 namespace ExpressionParser
 {
 AppExport Expression* parse(const App::DocumentObject* owner, const char* buffer);

src/App/Metadata.h

@@ -39,6 +39,12 @@
 namespace App
 {
 
+/**
+ * A namespace for metadata for Python external addons.
+ *
+ * This namespace contains functionality to define the contents of a
+ * package.xml file, such as Contact, License, Url, and Dependency.
+ */
 namespace Meta
 {
 

src/App/ProgramOptionsUtilities.h

@@ -28,6 +28,12 @@
 #include <array>
 #include <string>
 
+/**
+ * A namespace for utilities.
+ *
+ * Currently, this namespace contains functionality to define custom syntax to
+ * parse command line options.
+ */
 namespace App::Util
 {