Added contribution guidelines

[soumeh01]

Checklist

• 🤖 This change is covered by unit tests (if applicable).
• 🤹 Manual testing has been performed (if necessary).
• 🛡️ Security impacts have been considered (if relevant).
• 📖 Documentation updates are complete (if required).
• 🧠 Third-party dependencies and TPIP updated (if required).

[soumeh01]

@jreineckearm This is an initial version of the contribution guidelines. Please have a look at it . Feel free to make amends or improvements.

[jreineckearm]

LGTM, thanks! Great start for this.