Add README.md for each language

[clegaard]

Creating FMUs in various languages results slightly different workflows. For example an FMU implemented in python requires different runtime dependencies, compared to a statically compiled language such as C#.

A solution is to add language-specific README.md to each generated FMU.

For a Matlab FMU this could look like:

# Matlab FMU

## Installation Instructions

To use this FMU, you need:
- an installation of matlab
- a python interpreter with the following
  - matlab engine installed (instructions taken from [here](https://se.mathworks.com/help/matlab/matlab_external/install-the-matlab-engine-for-python.html))
    1. Make sure you have a python that's compatible with your matlab.
    2. Open an administrator's terminal at the Matlab's python installation directory. For example: C:\Program Files\MATLAB\R2021a\extern\engines\python
    3. Install the matlab engine (use `sudo` if on linux): `python .\setup.py install`
    4. Test the matlab engine by starting a python interpreter and running

    >>> import matlab.engine
    >>> eng = matlab.engine.start_matlab()
    >>> eng.plus(3,4)
    7
    ```

• packages described in requirements.txt installed
  1. Open a terminal in the current folder, and run: pip install -r requirements.txt

Editing and Launching the Matlab Code

The matlab code needs to be placed inside the matlabcode folder. An example "Adder FMU" is provided.

The launch.toml folder controls how to start the matlab_proxy.py script, which is the one that will automatically start and interact with matlab, when the FMU is instantiated.

Workflow to update the FMU:

1. Change the matlab code inside matlabcode folder
2. Update the modelDescription.xml according to the matlab code.
   1. Pay attention to the value references of the variables, and make sure these are consistent with the matlab code.
3. After the changes, zip the folder and change the extension to FMU.

[clagms]

Now fixed in https://github.com/INTO-CPS-Association/unifmu/tree/dev/claudio