feat(skip_secrets): add subject

subjects/devops/skip_secrets/README.md

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+## skip_secrets
+
+### Instructions
+
+You need to write a script, `skip_secrets.py`, that will be able to decrypt the text coming form a specific file.
+
+The script will receive a file name as the first argument, check if the file is readable, filter the content by skipping all the lines containing `pineapple` and save the result in a file `out.txt`
+
+If the file passed as argument is not readable or the number of arguments is not the one expected, the script should exit with a status code `1`.
+
+### Usage
+
+Below an example of how the script is supposed to work:
+
+```console
+$ cat -e file.txt
+A normal pizza $
+Another normal pizza$
+A pizza with pineapple$
+Yet another very normal and delicious pizza$
+$ python3 skip_secrets.py
+$ echo $?
+1
+$ python3 skip_secrets.py file.txt
+$ cat out.txt
+A normal pizza $
+Another normal pizza$
+A pizza with pineapple$
+Yet another very normal and delicious pizza$
+$
+```
+
+### Hints
+
+- It is possible to read arguments passed to a python script using the `sys` module. Here is an example of script (`argv.py`):
+
+```python
+import sys
+
+for argv in sys.argv:
+    print(argv)
+```
+
+And its output:
+
+```console
+$ python3 argv.py 1 2 3 something else
+argv.py
+1
+2
+3
+something
+else
+$
+```
+
+- It is possible to interrupt the execution of a script and returning a status code different from `0` with the function `exit()`. For example, consider the following `example.py`:
+
+```python
+exit(1)
+```
+
+This would be the result:
+
+```console
+$ python3 example.py
+$ echo $?  # check the status code
+1
+```
+
+### Reference
+
+[Python sys.argv](https://docs.python.org/3/library/sys.html#sys.argv)