add ja lcd api reference

docs/en/api_reference/micropython/peripherals/api_gpio.md

@@ -0,0 +1,23 @@
+# GPIO
+
+[中文](/zh_CN/api_reference/micropython/peripherals/api_gpio) | English | [日本語](/ja/api_reference/micropython/peripherals/api_gpio)
+
+*Refer to GPIO API of [Arduino](http://www.arduino.cc)*
+
+### <mark>digitalRead</mark>
+> uint32 digitalRead(uint8 pin);
+
+Read the value of `pin`
+
+| Param | Type | Description |
+| --- | --- | --- |
+| pin | <code>uint8</code> | the number of pin |
+
+Return:
+    digital level(0/1)
+
+**Example**
+```c++
+uint32_t pin21_data;
+pin21_data = digitalRead(21);
+```