Create a more appealing CONTRIBUTING.md template for our projects

## Problem

The current Contributing Guidelines seems a bit more of a grocery list, that I think contributors are bypassing this information. We want to make it easier to contributors

In my opinion, we should have separate sessions for every type of contribution we welcome: coding, manual testing, documentation, etc. Having this, we can provide specific guidelines for each type of contribution.

The idea here is to create a template for CONTRIBUTING.md and share it with the community.

- Example: [anitab-org/mentorship-android -> CONTRIBUTING.md](https://github.com/anitab-org/mentorship-backend/blob/develop/.github/CONTRIBUTING.md)
- [Ideas by Sakshi shared on Zulip](https://anitab-org.zulipchat.com/#narrow/stream/216326-documentation/topic/Documentation.20opportunity/near/198214835)

## Tasks

- [ ] Create a template for Contributing Guidelines