Update Contributing Guide (#561)

* Update and Add images

* Update Contributing.md

* Add images

* Update Contributing.md

* Minor in contributing.md

* Update CONTRIBUTING.md

Co-authored-by: Theofanis Petkos <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Theofanis Petkos <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Theofanis Petkos <[email protected]>

* Minor changes in Contributing Guide

* Update CONTRIBUTING.md

Co-authored-by: George Margaritis <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: George Margaritis <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: George Margaritis <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: George Margaritis <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: George Margaritis <[email protected]>

* Fix headers and links in Contributing.md

* Update CONTRIBUTING.md

Co-authored-by: Lysandros Nikolaou <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Lysandros Nikolaou <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Lysandros Nikolaou <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Lysandros Nikolaou <[email protected]>

* Update CONTRIBUTING.md

Co-authored-by: Lysandros Nikolaou <[email protected]>

* Add extra step

* Minor fix in CONTRIBUTING.md

* Update CONTRIBUTING.md

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Co-authored-by: Theofanis Petkos <[email protected]>
Co-authored-by: George Margaritis <[email protected]>
Co-authored-by: Lysandros Nikolaou <[email protected]>

Author: 4 people