Add RTC clock sample using seeed_xiao_expansion_board and SSD1306 display

[Yongci]

This PR adds a new sample application demonstrating how to use the Zephyr RTC API together with an SSD1306 OLED display to implement a simple real-time clock (RTC). The sample is designed to run on the xiao_ble board with the seeed_xiao_expansion_board shield.

Key features:

Initializes and sets current date/time using rtc driver.

Periodically reads time from RTC.

Displays updated time on an SSD1306 OLED using the character framebuffer (cfb) driver.

Runs without console output — output is only shown on the display.

Demo:

Hardware requirements:

XIAO BLE board

Seeed XIAO Expansion Board with SSD1306 (I²C interface)

Tested on:

xiao_ble + seeed_xiao_expansion_board

Tags: rtc, display, cfb, ssd1306, samples

[github-actions]

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[bjarki-andreasen]

fun sample :) it will need to be placed elsewhere though, there is no clock subsystem :) I will recommend placing it at samples/drivers/display_cfb

there are also quite a bit of formatting issues, check the guide here https://docs.zephyrproject.org/latest/contribute/style/index.html