Pinyin support for external keyboard

Test case.
- In System Settings > Language switch to Simplified Chinese.
- Attach an external keyboard (USB, Bluetooth).
- Open Notes.

Expected result.
- Pinyin can be used to enter Chinese characters with the external keyboard.

Actual result.
- There is currently no support for pinyin in external keyboards.

Comment by Tao Chen, who tested this: «We can set Chinese keyboard layout in system settings, but we cannot enter Chinese character directly by tapping the keyboard, it's because that there is no Chinese keyboard in china, we just use the English keyboard with letters "a, b, c, d...." which we call it "pinyin". And we also need input method installed to help us to enter Chinese characters».