Add mgos_gpio_read(); mgos_[mu]sleep()

unittest/mgos_mock.c

@@ -78,3 +78,11 @@ bool mgos_net_get_ip_info(enum mgos_net_if_type if_type, int if_instance, struct
 void mgos_net_ip_to_str(const struct sockaddr_in *sin, char *out) {
   return;
 }
+
+void mgos_usleep(uint32_t usecs) {
+  usleep(usecs);
+}
+
+void mgos_msleep(uint32_t msecs) {
+  usleep(1000 * msecs);
+}