Add Contribution guideline in Readme

CONTRIBUTING.md

@@ -0,0 +1,48 @@
+# General Contribution Guidelines
+
+1. If code changes are being made, please include documentation **following the guidelines in the Wiki** (typings are also welcome, but we can probably do them for you, given the documentation).
+2. (For the maintainers of this repo) Label PRs appropriately.
+3. Link relevant issues.
+4. Ensure compatibility with the latest changes in the repo.
+
+## Contributing to the Manim Community Fork - General instructions
+
+As this is a Fork of [Manim by 3b1b](https://github.com/3b1b/manim), contributing can be a bit confusing. Because of that, here is a small guide on it. 
+
+1. First, make a fork of this repository.
+2. Then clone the repository you forked using the command below (bash/zsh).
+
+ ```sh
+   git clone <your-fork-url>
+   cd manim
+ ```
+
+3. Now that you have cloned the repo, before making any changes, you have to enter the commands below in order to be able to contribute to Manim Community.
+
+   ```sh
+   git remote add fork https://github.com/ManimCommunity/manim.git
+   git fetch fork
+   git checkout -b <your-branch-name> fork/master
+   ```
+
+   The first command tells `git` that you are going to make a Pull Request to Manim Community. 
+   The second command pulls all the commits from the aforementioned fork.
+   Finally, the third one makes your current working branch up-to-date with Manim Community's master branch.
+
+    Now there are three repositories that git is keeping track of: the manim community repo (referred to as "fork"), your own fork of it (referred to by git as "origin"), and your local repository.
+
+4. After that, you can make your changes to the repo's files (the code is in the `manim` directory). Then, you can commit said changes.
+
+5. Finally, instead of  typing in `git push`, enter the command below.
+
+   ```sh
+   git push -u origin <your-branch-name>
+   ```
+
+   Doing so creates a new branch with the updated contents of your fork on GitHub.
+
+   Then you can make a Pull Request to the Manim Community Repo from your fork, through GitHub. Make sure to select `ManimCommunity/manim` instead of `3b1b/manim` as the `base repository` and your fork and branch as `head repository` - see the picture below.
+
+   ![pull-requests-example-manim-community](./readme-assets/pull-requests.PNG)
+
+Also make sure to pull from upstream/master right before making a Pull Request, resolve merge conflicts locally and only then submit the Pull Request.

README.md

@@ -252,7 +252,9 @@ Documentation is in progress at [eulertour.com/docs](https://www.eulertour.com/d
 The issues board is reserved for bugs, and future features planned for Manim. If you need help installing or using Manim, please take a look at [the Reddit Community](https://www.reddit.com/r/manim) or the [Discord Community](https://discord.gg/mMRrZQW)
 
 ## Contributing
-Is always welcome. In particular, there is a dire need for tests and documentation.
+Is always welcome. In particular, there is a dire need for tests and documentation. 
+
+For instructions, guidelines and other details, please check out the file [CONTRIBUTING.md](https://github.com/ManimCommunity/manim/blob/master/CONTRIBUTING.md).
 
 ## License