chore: enable colored output in CI logs

Set environment variables to force colored output for tools and disable
the interactive `tox` spinner. This improves the readability and
cleanliness of the GitHub Actions logs.

Author: rm-hull

.github/workflows/main.yml

@@ -9,6 +9,10 @@ on:
 jobs:
   build:
     runs-on: ${{ matrix.os }}
+    env:
+      FORCE_COLOR: 1
+      PY_COLORS: 1
+      TOX_PARALLEL_NO_SPINNER: 1
     strategy:
       matrix:
         os: [ubuntu-latest]