Add .gitignore file and refactor llcc68 component

- Added a comprehensive .gitignore file to exclude unnecessary files and directories for various platforms and tools.
- Removed the llcc68.cpp source file as part of the refactoring process.
- Updated llcc68.hpp to replace the `init_exti` function declaration with inline interrupt configuration logic.
- Changed `EXTI_PIN` to `EXTI_PINS` for clarity and consistency.
- Refactored the handling of CAD parameters and improved type safety by using `enum class` for `CAD_EXIT_MODE` and `CAD_SYMB`.

CMakeLists.txt

@@ -1,6 +1,5 @@
 idf_component_register(
         SRCS 
-                src/llcc68.cpp 
                 src/hal_spi.cpp
         INCLUDE_DIRS 
                 inc/