feat: add contributing guidelines

Author: sanjayankur31

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+To develop pyNeuroMatic, you can use the `dev` extra and the `development` branch:
+
+    git clone https://github.com/SilverLabUCL/pyneuromatic.git
+    cd
+    git checkout development
+    pip install .[dev]
+
+Please use pre-commit to run the pre-commit hooks.
+You will need to install the hooks once:
+
+    pre-commit install
+
+They will then run before each commit.
+
+We follow a pull request workflow.