Add more convenient constructors for I2C connection

ICM20948.h

@@ -215,6 +215,7 @@ class ICM20948 : public IMUInterface, public Logger
 	/* Constructors */
 	ICM20948(uint8_t addr = 0x68) : _wire{&Wire}, i2cAddress{addr}, useSPI{false} {}
 	ICM20948(TwoWire *w, uint8_t addr = 0x68) : _wire{w}, i2cAddress{addr}, useSPI{false} {}
+	ICM20948(TwoWire& w, uint8_t addr = 0x68) : _wire{&w}, i2cAddress{addr}, useSPI{false} {}
 	ICM20948(SPIClass& s, int cs = -1) : _spi{&s}, csPin{cs}, useSPI{true} {}
 
 	bool begin() override;

MPU9250.h

@@ -69,12 +69,10 @@ class MPU9250 : public IMUInterface, public Logger {
     WOM_RATE_500HZ = 0x0B
   };
   MPU9250() {}
-  MPU9250(TwoWire *i2c, const I2cAddr addr) :
-          imu_(i2c, static_cast<uint8_t>(addr)) {}
-  MPU9250(SPIClass *spi, const uint8_t cs = 255) :
-          imu_(spi, cs) {}
-  MPU9250(SPIClass& spi, const uint8_t cs = 255) :
-          imu_(&spi, cs) {}
+  MPU9250(TwoWire *i2c, const I2cAddr addr) : imu_(i2c, static_cast<uint8_t>(addr)) {}
+  MPU9250(TwoWire& i2c, const I2cAddr addr = I2C_ADDR_PRIM) : imu_(&i2c, static_cast<uint8_t>(addr)) {}
+  MPU9250(SPIClass *spi, const uint8_t cs = 255) : imu_(spi, cs) {}
+  MPU9250(SPIClass& spi, const uint8_t cs = 255) : imu_(&spi, cs) {}
   void config(TwoWire *i2c, const I2cAddr addr);
   void config(SPIClass *spi, const uint8_t cs);
   bool begin() override;

README.md

@@ -48,6 +48,23 @@ Notice, that MPU6500 does not include a magnetometer, so magnetometer data will
 
 You can also use `<MPU6500.h>` header and `MPU6500` class, which is an alias for `MPU9250` class.
 
+#### I²C
+
+In case of using I²C connection (not recommended), the initialization would look like this:
+
+```cpp
+#include <MPU9250.h>
+#include <Wire.h>
+
+MPU9250 IMU(Wire); // the default address is used automatically
+
+void setup() {
+  Wire.begin();
+  Wire.setClock(400000); // 400 kHz I²C clock
+  IMU.begin();
+}
+```
+
 ### ICM-20948
 
 The ICM-20948 IMU driver has the same interface. Only the declaration is changed in the example above: