chore(numerical_operations): add subject for new py exercise in scripting piscine

subjects/devops/numerical_operations/README.md

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+## Numerical operation
+
+### Instructions
+
+Create a file `numerical_operations.py` containing the following functions:
+
+- `add(a, b)`
+- `subtract(a, b)`
+- `multiply(a, b)`
+- `power(a, b)`
+- `square(a)`
+
+We assume that `a` and `b` are numbers (`int` or `float`).
+
+### [Optional] Use a virtual environnement to run python code locally
+
+Virtual environments can help you to run your code locally.
+
+[Learn all you need about virtual environments](https://openclassrooms.com/fr/courses/6951236-mettez-en-place-votre-environnement-python/7013854-decouvrez-les-environnements-virtuels).
+
+Here, we setup a virtual environment with Miniconda.
+
+First, [download and install Miniconda](https://docs.conda.io/en/latest/miniconda.html).
+
+Then, use those commands to create a new environment:
+
+```bash
+# create a new virtual environment for python 3.10
+$ conda create --name my_env python=3.10
+
+# activate your new environment
+$ conda activate my_env
+
+# From now, all python command use this python version in this terminal
+$ python --version
+Python 3.10.4
+```
+
+> We advise you to create one virtual environment per python project. Later, we could also install external packages on our environment.
+
+### Usage
+
+Here is a possible `test.py` to test your functions:
+
+```python
+import numerical_operations
+
+print(numerical_operations.add(2, 2))
+print(numerical_operations.subtract(10, 5))
+print(numerical_operations.multiply(3, 4))
+print(numerical_operations.power(3, 3))
+print(numerical_operations.square(3))
+```
+
+```bash
+$ python test.py
+4
+5
+12
+27
+9
+$
+```
+
+### Hints
+
+- You could `import math` at the start of your file to use the functions defined in that library (for example `math.sqrt()`).
+
+### References
+
+- [Square root in Python](https://www.geeksforgeeks.org/python-math-function-sqrt/)
+- [Operations in Python](https://www.geeksforgeeks.org/python-arithmetic-operators/)