Updated README, requirements and installation explanations.

- Added the Black badge to the README.md file.
- Replaced "requirements.yml" with "environment.yml" in the installation instructions.
- Added the sphinx version to the requirements.txt file.

Author: NanneD

README.md

@@ -1,4 +1,5 @@
 ![ELASPY logo](doc/_static/ELASPY_light.svg)
+[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 # ELASPY
 

doc/installation/installation.rst

@@ -19,7 +19,7 @@ You can easily download all files from the GitHub repository. Follow these steps
    
    cd documents/ELASPY
 
-5. Use an environment manager to create an environment in which you can run the code, such as `Anaconda <https://anaconda.org>`_ or `Miniconda <https://docs.anaconda.com/miniconda/>`_. You can use the following command to create an environment called ``ELASPY`` by using the ``requirements.yml`` file that is also part of your ``ELASPY`` folder:
+5. Use an environment manager to create an environment in which you can run the code, such as `Anaconda <https://anaconda.org>`_ or `Miniconda <https://docs.anaconda.com/miniconda/>`_. You can use the following command to create an environment called ``ELASPY`` by using the ``environment.yml`` file that is also part of your ``ELASPY`` folder:
 
 .. code-block:: shell
 
@@ -51,7 +51,7 @@ Manually
    
    cd documents/ELASPY
 
-5. Use an environment manager to create an environment in which you can run the code, such as `Anaconda <https://anaconda.org>`_ or `Miniconda <https://docs.anaconda.com/miniconda/>`_. You can use the following command to create an environment called ``ELASPY`` by using the ``requirements.yml`` file that can be downloaded from the GitHub repository:
+5. Use an environment manager to create an environment in which you can run the code, such as `Anaconda <https://anaconda.org>`_ or `Miniconda <https://docs.anaconda.com/miniconda/>`_. You can use the following command to create an environment called ``ELASPY`` by using the ``environment.yml`` file that can be downloaded from the GitHub repository:
 
 .. code-block:: shell
 

requirements.txt

@@ -8,4 +8,5 @@ pytest==7.3.1
 pluggy==1.0.0
 mypy==0.981
 pydata-sphinx-theme==0.15.3
-sphinx-design==0.6.0
+sphinx-design==0.6.0
+sphinx==5.0.2