Add Japanese Era (Wareki) Display Feature

[kbc-yam]

I have created a program to display the Japanese Era (Wareki) for users in Japan. The Japanese Era is a unique way of representing years in Japan.

Due to the possibility of sudden changes in the Japanese Era, local watch manufacturers in Japan have faced challenges in adding a Wareki display feature to their timepieces.

This pull request introduces the Wareki display functionality to address this issue for Japanese users. The implementation includes handling sudden changes in the Japanese Era to ensure accurate and up-to-date information.

Please review and consider merging this pull request to enhance the user experience for Japanese customers.

[kbc-yam]

The displayed Japanese Era can be changed by the buttons on the watch, making it also usable as a converter between the Gregorian calendar and the Japanese Era.

• Light button: Subtract one year from the Japanese Era.
• Start/Stop button: Add one year to the Japanese Era.

Button operations support long-press functionality.

Japanese Era Notations:

• r : REIWA (令和)
• h : HEISEI (平成)