Add pre-commit configuration to the cookiecutter template.

This uses the same configuration from
https://github.com/adafruit/Adafruit_CircuitPython_TestRepo, using
pre-commit instead of black as part of the CI.

Author: Flameeyes

{{ cookiecutter.library_name }}/.github/workflows/build.yml

@@ -42,14 +42,14 @@ jobs:
       # (e.g. - apt-get: gettext, etc; pip: circuitpython-build-tools, requirements.txt; etc.)
       run: |
         source actions-ci/install.sh
-    - name: Pip install pylint, black, & Sphinx
+    - name: Pip install pylint, Sphinx, pre-commit
       run: |
-        pip install --force-reinstall pylint black==19.10b0 Sphinx sphinx-rtd-theme
+        pip install --force-reinstall pylint Sphinx sphinx-rtd-theme pre-commit
     - name: Library version
       run: git describe --dirty --always --tags
-    - name: Check formatting
+    - name: Pre-commit hooks
       run: |
-        black --check --target-version=py35 .
+        pre-commit run --all-files
     - name: PyLint
       run: |
         pylint $( find . -path './adafruit*.py' )

{{ cookiecutter.library_name }}/.pre-commit-config.yaml

@@ -0,0 +1,19 @@
+# SPDX-FileCopyrightText: 2020 Diego Elio Pettenò
+#
+# SPDX-License-Identifier: Unlicense
+
+repos:
+-   repo: https://github.com/python/black
+    rev: 19.10b0
+    hooks:
+    - id: black
+-   repo: https://github.com/fsfe/reuse-tool
+    rev: latest
+    hooks:
+    - id: reuse
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.3.0
+    hooks:
+    -   id: check-yaml
+    -   id: end-of-file-fixer
+    -   id: trailing-whitespace

{{ cookiecutter.library_name }}/pyproject.toml

@@ -0,0 +1,6 @@
+# SPDX-FileCopyrightText: 2020 Diego Elio Pettenò
+#
+# SPDX-License-Identifier: Unlicense
+
+[tool.black]
+target-version = ['py35']