feat: add an option to contribute stories under the [x people have benefitted from this book] section (testimonials).

[yehiarasheed]

Description

Following up on issue #667, there is a section that starts with the heading Over 1,000,000 people have benefitted from this handbook!, under which are some stories concerning how beneficial this handbook is. The newest story was published in 2022, so over 2 years ago now. To keep the website alive and filled up with newer stories and testimonials, I suggest that we could add the option for users to share under this section, just like how we've added this option under the Success stories Section with the Would you like to contribute a success story? Open a Pull Request here! text. More on this in the screenshots below but my point is, we would still get to select the stories to be added, with the added benefit of keeping them updated. I will follow up on this issue with a PR.

Screenshots