Add pio onewire example (#334)

* Adds PIO onewire example

Co-authored-by: martin <admin@crossleys.biz>

pio/onewire/onewire_library/CMakeLists.txt

@@ -0,0 +1,18 @@
+add_library(onewire_library INTERFACE)
+target_sources(onewire_library onewire_library.c)
+
+# invoke pio_asm to assemble the state machine programs
+#
+pico_generate_pio_header(onewire_library ${CMAKE_CURRENT_LIST_DIR}/onewire_library.pio)
+
+target_link_libraries(onewire_library INTERFACE
+        pico_stdlib
+        hardware_pio
+        )
+
+# add the `binary` directory so that the generated headers are included in the project
+#
+target_include_directories(onewire_library INTERFACE
+	${CMAKE_CURRENT_SOURCE_DIR}
+	${CMAKE_CURRENT_BINARY_DIR}
+	)