Add usage guidelines

Signed-off-by: Ryan Friedman <ryanfriedman5410+github@gmail.com>

CMakeLists.txt

@@ -206,6 +206,7 @@ endif()
 
 # Export old-style CMake variables for includes
 ament_export_include_directories("include/${PROJECT_NAME}")
+ament_export_libraries(${interface_targets} ${plugin_targets})
 
 # Export modern CMake targets
 ament_export_targets(export_${PROJECT_NAME} HAS_LIBRARY_TARGET)

README.md

@@ -0,0 +1,20 @@
+# Filters
+
+## Usage with ament_cmake
+
+Here is recommended approach on how to link `filters` to your project, using the `filter_base` target.
+
+```cmake
+find_package(filters CONFIG REQUIRED)
+
+add_library(my_library)
+# Other library stuff here
+
+target_link_libraries(my_library PUBLIC filters::filter_base)
+```
+
+Do NOT use the `filters_LIBRARIES` anymore.
+
+For more information, 
+see the [ament_cmake](https://docs.ros.org/en/rolling/How-To-Guides/Ament-CMake-Documentation.html)
+tutorial.