[EXTERNAL] add strings to forbidden

[sagarishere]

every exercise can currently be solved by using strings for example

strings bin | grep "modified"

to give the message required to complete the exercise.

However, that technique will teach us nothing about binary inspection, reverse engineering or binary manipulation.

Before starting, please choose the relevant pull request Labels, Reviewers, and Assignees

DEV-#### | SUP-#### | CON-####

Why?

It is important to learn concepts, not circumvent the exercise.

Solution Overview

Explicitly forbid strings command

Implementation Details

Added one line to README

Build Images

Please assign the label 📦 build If you want to re-build the following test images:

• 💻 Sh
• 🚀 JS
• 🧩 DOM