Add CAN communication and GPIO control functionality

- Created HAL configuration file for STM32F1xx (stm32f1xx_hal_conf.h).
- Added interrupt handler definitions in stm32f1xx_it.h.
- Implemented CAN initialization and configuration in can.c.
- Configured GPIO pins for output and external interrupts in gpio.c.
- Developed main application logic in main.c for toggling an LED and sending CAN messages.
- Implemented MSP initialization and de-initialization for CAN in stm32f1xx_hal_msp.c.
- Defined interrupt service routines in stm32f1xx_it.c for CAN and EXTI interrupts.
- Added README for project-specific libraries and PlatformIO configuration.
- Created platformio.ini for project build settings.
- Added stm32pio.ini for CubeMX integration with PlatformIO.
- Included README for testing directory to guide unit testing setup.

firmware/components/can_testing/canblinker/stm32pio.ini

@@ -0,0 +1,18 @@
+[app]
+platformio_cmd = platformio
+cubemx_cmd = /opt/stm32cubemx/STM32CubeMX
+java_cmd = java
+
+[project]
+cubemx_script_content = config load ${ioc_file_absolute_path}
+	generate code ${project_dir_absolute_path}
+	exit
+platformio_ini_patch_content = [platformio]
+	include_dir = Inc
+	src_dir = Src
+board = bluepill_f103c8
+ioc_file = CAN-B.ioc
+cleanup_ignore = CAN-B.ioc
+cleanup_use_git = False
+inspect_ioc = True
+