feat(docs): Added Conventional-Commits guidelines to the CONTRIBUTING.md (OPTION 2)

[ItsIgnacioPortal]

As discussed in #1020

There's two ways of options for implementing the conventional-commits syntax into Seclists.

This is option 2

I've made a flowchart using mermaid, which is officially supported in github markdown. Then, I added it into the CONTRIBUTING.md file directly.

Benefits of this implementation:

1. Cohesiveness: The mermaid format is rendered in such a way that it follows the github website style, making the whole CONTRIBUTING.md document more cohesive with the github styling.
2. Selectable text: Contributors will be able to copy-paste the recommended syntaxes directly, facilitating their use of conventional-commits syntax in their contributions.

View the resulting CONTRIBUTING.md file

Now compare this with option 1: #1043