DOC: Add instructions for contributing to Cartopy

Set up a development environment and outline the steps required
for contributing code.

docs/source/contribute.rst

@@ -0,0 +1,47 @@
+.. _contribute:
+
+Contributing to Cartopy
+=======================
+
+Cartopy is an open-source project that welcomes contributions from anyone. A good place
+to start contributing is by fixing typos, adding examples, or improving the explanations
+of the functions.
+
+To contribute new features or bug fixes, you can create a pull request with your code changes
+on GitHub. The easiest way to get started contributing code is to clone the repository to your
+local system and install the conda development environment included with the source code.
+
+.. code::
+
+  git clone git@github.com:YOUR-USERNAME/cartopy.git
+  cd cartopy
+
+  conda env create -f environment.yml
+  conda activate cartopy-dev
+
+This will install all of the required dependencies for compiling the code, running the tests, and
+building the documentation. Remember to activate the `cartopy-dev` environment.
+
+A development and test workflow may look something like the following code block.
+
+.. code::
+
+  # Activate your development environment
+  conda activate cartopy-dev
+
+  # Checkout a new feature branch
+  git checkout -b my-cool-feature
+
+  # Make your code changes here, including tests for the changes!
+  # add and commit the changes with a useful commit message
+  # describing what changes you made
+  git add lib/cartopy/my-changed-file.py
+  git commit
+
+  # Test your code on 4 processors
+  pytest -n 4 lib/cartopy
+
+  # push your changes to your GitHub account
+  git push --set-upstream origin my-coll-feature
+
+  # Go to GitHub and make a Pull Request to Cartopy

docs/source/getting_started/index.rst

@@ -28,6 +28,7 @@ attributions for data, and becoming a contributor on the project.
 
 .. toctree::
 
+    ../contribute
     ../citation
     ../copyright
     ../contributors

docs/source/index.rst

@@ -49,5 +49,5 @@ There are many ways to get involved in the development of cartopy:
  * Contribute to the documentation fixing typos, adding examples, explaining things more clearly, or even
    re-designing its layout/logos etc. The `documentation source <https://github.com/SciTools/cartopy>`_ is kept in the same repository as the source code.
  * Contribute bug fixes (:issues:`a list of outstanding bugs can be found on GitHub <Type%3A%20bug>`).
- * Contribute enhancements and new features on the issue tracker.
+ * :ref:`contribute` describes some simple steps to get started when contributing code to Cartopy.
  * Chat with users and developers in the `Gitter chat room <https://gitter.im/SciTools/cartopy>`_.