update contributing guidelines twitter#129

Updated CONTRIBUTING.md file with new guidelines

README.md

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 [install]: https://gohugo.io/getting-started/installing/
 [run]: https://gohugo.io/getting-started/usage/
 [update some repo data]: ./.github/workflows/update-data.yml
+
+# Contributing Guidelines
+
+We welcome contributions to this project! Before getting started, please read these guidelines.
+
+## Git and GitHub
+
+First, it's important to understand the difference between Git and GitHub. Git is a version control system that allows you to track changes to your code over time. GitHub is a web-based platform that allows you to store and manage Git repositories, collaborate with others, and contribute to open source projects.
+
+## Cloning and Forking
+
+To contribute to this project, you will need to clone or fork the repository. Cloning creates a copy of the repository on your local machine, while forking creates a copy of the repository on your GitHub account. Here's how to do it:
+1. To clone the repository, run the following command in your terminal :  
+
+   `git clone https://github.com/twitter/opensource-website.git`  
+
+2. To fork the repository, click the "Fork" button on the top right corner of the repository page on GitHub.
+
+## Creating a Branch and Pushing Changes
+Before making any changes to the code, create a new branch to work on. This keeps your changes separate from the main codebase and makes it easier to merge your changes later. Here's how to do it :
+1. To create a new branch, run the following command in your terminal :
+
+   `git checkout -b new-branch-name`  
+
+   Replace "new-branch-name" with a descriptive name for your branch.  
+
+2. Make your changes to the code.  
+
+3. To push your changes to the repository, run the following command :
+
+   `git push origin new-branch-name`  
+
+   This will create a new branch on GitHub and push your changes to it.
+
+## Creating a Pull Request
+Once you've made your changes and pushed them to your branch, it's time to create a pull request (PR) to merge your changes into the main codebase. Here's how to do it:
+
+1. Go to the repository page on GitHub.  
+
+2. Click the "New pull request" button.
+
+3. Select your branch as the "compare" branch and the main branch as the "base" branch.
+
+4. Give your PR a descriptive title and description.
+> Good pull requests - patches, improvements, new features - are a fantastic
+help. They should remain focused in scope and avoid containing unrelated
+commits.
+
+5. Click the "Create pull request" button.
+
+6. Wait for a maintainer to review and merge your changes.
+
+## Squashing Commits
+If you've made multiple commits to your branch, it's a good idea to squash them into a single commit before creating a PR. This keeps the commit history clean and makes it easier to understand the changes you've made. Here's how to do it:
+
+1. Run the following command to open the interactive rebase tool :  
+
+   `git rebase -i HEAD~n`  
+
+   Replace "n" with the number of commits you want to squash.  
+
+2. In the editor that opens, replace "pick" with "squash" or "s" for the commits you want to squash.  
+
+3. Save and close the file.  
+
+4. In the editor that opens, write a new commit message for the squashed commit.  
+
+5. Save and close the file.  
+
+6. Run the following command to force push your changes to your branch :
+
+   `git push --force origin new-branch-name`  
+
+## Updating the Forked and Local Repository
+
+As updates are made to the original codebase, it is essential to keep your forked and local repositories up-to-date. To update the forked repository, use the `git fetch` command to fetch the changes from the upstream repository. Then, use the git merge command to merge the changes into your local repository. Finally, use the `git push` command to push the changes to your forked repository.
+
+To update the local repository, use the `git pull` command to fetch and merge the changes from the upstream repository into your local repository.