chapters/exploitation-techniques: Add Dockerfile for 07-challenge-shellcode-on-stack

[gabrielmocanu]

Description:

Create a Dockerfile for 07-challenge-shellcode-on-stack exercise.

Requirements:

1. Use a multi-stage Dockerfile:

• Build Stage:
  - Compile the provided C code into an executable.
• Runtime Stage:
  - Run the compiled executable and ensure it listens or operates on port 31345 .

2. Verify the functionality of the solution to ensure that it works as expected after building and running the Dockerfile.

3. Ensure the Dockerfile is optimized and avoids unnecessary layers.

Expected Outcome:

A fully working Dockerfile that can be built and executed in two separate stages, satisfying the above requirements.