Add pio onewire example (#334)

* Adds PIO onewire example

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

pio/onewire/CMakeLists.txt

@@ -0,0 +1,15 @@
+add_executable(pio_onewire)
+
+target_sources(pio_onewire PRIVATE onewire.c)
+
+add_subdirectory(onewire_library)
+
+target_link_libraries(pio_onewire PRIVATE
+    pico_stdlib
+    hardware_pio
+    onewire_library)
+
+pico_add_extra_outputs(pio_onewire)
+
+# add url via pico_set_program_url
+example_auto_set_url(pio_onewire)