This feature is not yet tested on the Append:: functions since not all
functions are yet implemented. As soon as they get implemented, this
feature will be verified on them as well.
Furthermore, a Clear function is added.
Finally, in this commit, mouse_left, mouse_right, mouse_middle, and mouse_double got
abbreviated to left, right, middle, and double.
Furthermore, I did a small refactoring of the naming conventions for the
enum functions. Instead of vague terms liek value and string, they are
now called u8_to_enum, str_to_enum, or enum_to_str.
Application is now able to set the types (Key, Mouse, MouseKey, String),
which are saved in a struct, with a function. Furthermore, the
application can check the returned type of the board with a match.
This commit also implements the append string functionallity.