feat: add branch termination check & crashes #97

Add the necessary things in order to make sure that every function ends with a termination statement that follows:

• return statement: Returns a value. Can be suppressed if the block doesn't return anything
• crash statement: Crashes the program instantly, doesn't cleanly unroll values.
• branch jump: Jumps to another branch/block

Furthermore, add MIR checks to make sure that every block ends with a termination statement. This is to guarantee behavior and allow LLVM and other bridges to fully optimize stuff

A crash can be done trough the following:

crash("This program will crash now");

A crash will instantly crash the program and exit it