Add a couple of examples of using the Max7219 LED driver chip (#209)

spi/max7219_32x8_spi/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_executable(max7219_32x8_spi
+        max7219_32x8_spi.c
+        )
+
+# pull in common dependencies and additional spi hardware support
+target_link_libraries(max7219_32x8_spi pico_stdlib hardware_spi)
+
+# create map/bin/hex file etc.
+pico_add_extra_outputs(max7219_32x8_spi)
+
+# add url via pico_set_program_url
+example_auto_set_url(max7219_32x8_spi)