Started some DHT22 stuff

Haven't tested it at all

components/dht22/dht22.h

@@ -1,10 +1,18 @@
 #pragma once
 
+#include <stdint.h>
+
 typedef enum {
-  DHT_OK
+  DHT22_OK,
+  DHT22_TIMING_ERROR,
+  DHT22_CHECKSUM_ERROR,
 } dht22_error;
 
-int dht_temperature();
-dht22_error dht_read();
+typedef uint16_t deci_percent;
+typedef int16_t  deci_degrees_c;
+
+deci_percent dht22_relative_humidity();
+deci_degrees_c dht22_temperature();
+dht22_error dht22_read();