add black pill definition from https://github.com/kylemccreery/zmk/tree/hid/app/boards/shields/rbf/boards

zmk-config/config/boards/arm/blackpill/blackpill_f401ce.conf

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+CONFIG_USE_DT_CODE_PARTITION=y

zmk-config/config/boards/arm/blackpill/blackpill_f401ce.overlay

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+/*
+ * Copyright (c) 2021 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+/ {
+	model = "stm32f401 blackpill board";
+	compatible = "st,stm32f401_blackpill", "st,stm32f401";
+
+	chosen {
+		zephyr,code-partition = &code_partition;
+		zephyr,console = &usart2;
+		zephyr,sram = &sram0;
+		zephyr,flash = &flash0;
+	};
+
+	leds {
+		compatible = "gpio-leds";
+		blue_led_1: led_1 {
+			gpios = <&gpioc 13 GPIO_ACTIVE_HIGH>;
+			label = "User LED";
+		};
+	};
+
+	aliases {
+		led0 = &blue_led_1;
+	};
+};
+
+&rtc {
+	status = "okay";
+};
+
+&usbotg_fs {
+	status = "okay";
+};
+
+&usart2 {
+	current-speed = <11500>;
+	status = "okay";
+};
+
+&flash0 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		boot_partition: partition@0 {
+			label = "tinyuf2_boot";
+			reg = <0x00000000 0x00004000>;
+		};
+		
+		storage_partition: partition@4000 {
+			label = "storage";
+			reg = <0x00004000 0x0000b000>;
+		};
+		
+		code_partition: partition@10000 {
+			label = "code_partition";
+			reg = <0x00010000 0x00030000>;
+		};
+	};
+};