Simplify build and test package distribution

.github/workflows/build.yml

@@ -20,15 +20,7 @@ on:
 jobs:
   build:
     name: Build and test package distribution
-    runs-on: ${{ matrix.os }}
-
-    # The maximum number of minutes to let a workflow run
-    # before GitHub automatically cancels it. Default: 360
-    timeout-minutes: 30
-
-    strategy:
-      matrix:
-        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    runs-on: ubuntu-latest
 
     steps:
       - name: Checkout code

CONTRIBUTING.rst

@@ -1,7 +1,7 @@
 Contributing
 ============
 
-If you would like to contribute to django-environ, please take a look at the
+If you would like to contribute to ``django-environ``, please take a look at the
 `current issues <https://github.com/joke2k/django-environ/issues>`_.  If there is
 a bug or feature that you want but it isn't listed, make an issue and work on it.
 
@@ -24,7 +24,7 @@ Guidelines for bug reports:
 * **Use the GitHub issue search** — check if the issue has already been
   reported.
 * **Check if the issue has been fixed** — try to reproduce it using the latest
-  main or develop branch in the repository.
+  ``main`` or ``develop`` branch in the repository.
 * Isolate the problem — create a reduced test case and a live example.
 
 A good bug report shouldn't leave others needing to chase you up for more
@@ -54,7 +54,7 @@ project:
 1. Check for open issues or open a fresh issue to start a discussion around a
    feature idea or a bug.
 2. Fork `the repository <https://github.com/joke2k/django-environ>`_
-   on GitHub to start making your changes to the develop branch
+   on GitHub to start making your changes to the ``develop`` branch
    (or branch off of it).
 3. Write a test which shows that the bug was fixed or that the feature works as
    expected.