use ruff linter and formatter

examples/javascript/js_example/views.py

@@ -2,7 +2,7 @@ from flask import jsonify
 from flask import render_template
 from flask import request
 
-from js_example import app
+from . import app
 
 
 @app.route("/", defaults={"js": "fetch"})

examples/javascript/pyproject.toml

@@ -27,3 +27,6 @@ filterwarnings = ["error"]
 [tool.coverage.run]
 branch = true
 source = ["js_example", "tests"]
+
+[tool.ruff]
+src = ["src"]