ppr1: add crude version of charge controller driver

src/nrf52/BQ25713.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <Arduino.h>
+
+/**
+ * Driver class to control/monitor BQ25713 charge controller
+ */
+class BQ25713 {
+    static const uint8_t devAddr;
+
+public:
+
+    /// Return true for success
+    bool setup();
+
+private:
+    uint16_t readReg(uint8_t reg);
+
+    /// Return true for success
+    bool writeReg(uint8_t reg, uint16_t v);
+};
+