CMake Inteface implementation

[EndrII]

See: #28

Note: Merge After #29

Description of Changes:

Added support for CMake projects.

Added a CMake Interface library that collects data from the C and Rust implementations and makes it available to any C++/C projects.

BackEnd Implementation Selection:

The BackEnd implementation can be chosen using the following CMake options:

option(OPENSIMPLEX_C "Enable building the legacy C implementation instead of Rust" ON)

option(OPENSIMPLEX_RUST "Enable building the Rust implementation" ON)

By default, only the Rust implementation is enabled.