Python Library

See merge request mgautierfr/lisa!4

Because this is what is installed in `rust:latest` image.

We must return runtimeError instead of panic or return default things.

We also need to convert this runtimeError to a python runtimeError.

Do not use the python's SyntaxError as it is not a Python syntax error but
a lisa one.

There is still a lot of work to do to correctly handle error.
(Remove all unwrap and unreachable)

Python

See merge request mgautierfr/lisa!3

It is a first step to have useful program.

Until now, parsing errors were discarded with the unwrap.

Now, we are not discarding it.
We are using the filter_map function to correctly parse the line and
return the error if needed and skip the empty lines.

The `Result` can be constructed from a iterator so we are propagating the
error when we '?'using the instructions.

It is technically possible to parse a source code and execute it.
But without being able to pass a custom Library or get the resulting
state, it is pretty useless.

The `Program` struct is only a container. It does nothing but having
reference to a `Library` and it doesn't help with python wrapping.

They somehow are identical. It is just that `If` takes a boolean test and
run the child branch once where the `Loop` takes a integer and run the
child branch several times.

And move Instruction in the instruction module now that it doesn't do
anything.

There is no more a notion of a block (it is a separated instruction list).

The list of instruction becomes a linked list.

It add a bit more work on the parsing part to create that list,
but it simplify a lot the interpreter.

The `Instruction` is no more a trait. It is a struct containing an
enum for the specific part.
This allow the instruction to have common fields as `line` and `indent`.


The code specific to the execution of a instruction is moved to the
interpreter.

This is not really an instruction and it simplify everything.

A program is a list of instruction, not a list of line.

We simplify the code by storing the right thing.

Add small binary

See merge request mgautierfr/lisa!2

The binary is a small sample binary to show how to use the lisa library
or how to write lisa program.

Add a simple ci

See merge request mgautierfr/lisa!1

This way, we avoid the explicit duplicate methods.

A `State` represent the state of a program (variables...).
The cl represent where we are in the program.