Add pre-commit hooks

.pre-commit-config.yaml

@@ -0,0 +1,30 @@
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.4.0
+    hooks:
+    # Identify invalid files
+    -   id: check-ast
+    -   id: check-json
+    -   id: check-yaml
+
+    # git checks
+    -   id: check-merge-conflict
+    -   id: check-added-large-files
+    -   id: check-case-conflict
+
+    # Python checks
+    -   id: check-docstring-first
+    -   id: requirements-txt-fixer
+    -   id: fix-byte-order-marker
+
+    # General quality checks
+    -   id: mixed-line-ending
+    -   id: trailing-whitespace
+        args: [--markdown-linebreak-ext=md]
+    -   id: check-executables-have-shebangs
+    -   id: end-of-file-fixer
+
+-   repo: https://github.com/pycqa/flake8
+    rev: 6.0.0
+    hooks:
+    -   id: flake8

CONTRIBUTING.md

@@ -75,10 +75,16 @@ Komikku can be built in a Python virtual environment. However, some tools and de
     ```sh
     # Create venv
     python3 -m venv .venv
+
     # Activate venv
     source .venv/bin/activate
+
     # Install dependencies
     pip install -r requirements.txt
+    pip install -r requirements-dev.txt
+
+    # Install pre-commit hooks
+    pre-commit install
     ```
 
     NOTE: Python package `file-magic` is an possible alternative to `python-magic`.

requirements-dev.txt

@@ -0,0 +1,5 @@
+flake8
+pre-commit
+pycodestyle
+pytest
+pytest-steps