add keypad matrix driver

README.md

@@ -265,6 +265,7 @@ have achieved the "released" status (published on crates.io + documentation / sh
 11. [TSL256X] - I2C - Light Intensity Sensor - [Intro blog post][11] - ![crates.io](https://img.shields.io/crates/v/tsl256x.svg)
 12. [EEPROM24x] - I2C - 24x series serial EEPROM driver - [Intro blog post][12] - ![crates.io](https://img.shields.io/crates/v/eeprom24x.svg)
 13. [DS1307] - I2C - Real-time clock driver - [Intro blog post][13] - ![crates.io](https://img.shields.io/crates/v/ds1307.svg)
+14. [keypad] - GPIO - Keypad matrix circuits - [Intro post][14] - ![crates.io](https://img.shields.io/crates/v/keypad.svg)
 
 [L3GD20]: https://crates.io/crates/l3gd20
 [LSM303DLHC]: https://crates.io/crates/lsm303dlhc
@@ -302,6 +303,9 @@ have achieved the "released" status (published on crates.io + documentation / sh
 [DS1307]: https://crates.io/crates/ds1307
 [13]: https://blog.eldruin.com/ds1307-real-time-clock-rtc-driver-in-rust/
 
+[keypad]: https://crates.io/crates/keypad
+[14]: https://www.reddit.com/r/rust/comments/9j42o9/weekly_driver_keypad_matrix_circuits/
+
 *NOTE* You may be able to find even more driver crates by searching for the [`embedded-hal-driver`]
 keyword on crates.io!