Docs: Fix links in the README

[adiati98]

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Description

We have changed the link to our courses' website. So, we need to update the links to the course in the README of the guestbook repo.

Suggested Solution

Below, you will find the lines that need to be updated and how they need to be updated.

• guestbook/README.md

  Line 12 in f539a0c

  This guestbook is a place for people who have taken [OpenSauced](https://app.opensauced.pizza/)'s [Intro to Open Source course](https://intro.opensauced.pizza/#/intro-to-oss/README) to take their first steps into contributing to open source.

  [Intro to Open Source course](https://opensauced.pizza/learn/intro-to-oss/)

• guestbook/README.md

  Line 16 in 10db621

  For complete instructions on how to add yourself to our guest book, please head to the "[Let's Get Practical](https://intro.opensauced.pizza/#/05-how-to-contribute-to-open-source?id=let39s-get-practical)" section in our Intro to Open Source course.

  "[Let's Get Practical](https://opensauced.pizza/learn/intro-to-oss/how-to-contribute-to-open-source#lets-get-practical)"

• guestbook/README.md

  Line 20 in 10db621

  If you encounter merge conflicts while contributing to this repository, read our Intro to Open Source course's "[Merge Conflicts in the Guestbook Repository](https://intro.opensauced.pizza/#/05-how-to-contribute-to-open-source?id=merge-conflicts-in-the-guestbook-repository)" section.

  "[Merge Conflicts in the Guestbook Repository](https://opensauced.pizza/learn/intro-to-oss/how-to-contribute-to-open-source#merge-conflicts-in-the-guestbook-repository)"

• guestbook/README.md

  Line 32 in 10db621

  - **Course improvement**: If you are interested in improving OpenSauced's Intro to Open Source course, please create an issue at our [intro repository](https://github.com/open-sauced/intro) and refer to the [Contributing Guidelines](https://github.com/open-sauced/intro/blob/main/CONTRIBUTING.md).

  [Contributing Guidelines](https://github.com/open-sauced/intro/blob/main/contributing/CONTRIBUTING.md)

[Harshh18]

Kindly assign me this issue, I would love to contribute to this repository.

[adiati98]

Hey @Harshh18,
Thank you for your interest in working on this issue. ✨

Please read our contributing guidelines to contribute to this repository.

[Harshh18]

Okay, thank you, I'll start working on this