chore: adds contribution guidelines

CONTRIBUTING.md

@@ -0,0 +1,35 @@
+# How to contribute to `validators`
+
+Hi, to start, you need the following installed on your system.
+
+1. [Git](https://git-scm.com/)
+2. [Python](https://www.python.org/) v3.8 or later and
+3. [PDM](https://pdm-project.org/en/stable/) for easy dependency management.
+4. (Optional/Recommended) NodeJS for type checking.
+5. (Optional/Recommended) [mise](https://github.com/jdx/mise) to manage multiple versions of Python, NodeJS etc.
+
+
+First [fork](https://github.com/python-validators/validators/fork) this repository. Then clone it to your system. Then install development dependencies.
+
+
+```sh
+# cloning repository
+$ git clone "https://github.com/YOUR_USERNAME/validators.git"
+# changing directory 
+$ cd validators
+# installing development dependencies
+$ pdm install
+```
+
+Activate the virtual environment and run `tox` to verify test cases.
+
+```sh
+# activate virtual environment
+$ . ./.venv/bin/activate # replace `/bin/` with `/Scripts/` if you're on Windows.
+# run tox for linting, type checking, formatting etc.
+$ tox
+```
+
+Create a git branch. You can now make changes to the source code. If needed, test your change by running `pytest`. Commit, push and create a pull request.
+
+If you're in doubt feel free to start a discussion [here](https://github.com/python-validators/validators/discussions). Thanks for taking interest in this library.