Default to ruff-version from pyproject.toml (#30)

Closes: #9 

Changes the default behavior to:

- Search for a pyproject.toml in the repo root
- Search in project.dependencies and dependency-groups.dev for ruff
- If none is found use latest

Support for requirements.txt files can be added later

__tests__/fixtures/pyproject-dependency-dev-project/pyproject.toml

@@ -0,0 +1,15 @@
+[project]
+name = "pyproject-dependency-dev-project"
+version = "0.1.0"
+description = "Add your description here"
+readme = "README.md"
+requires-python = ">=3.12"
+
+[dependency-groups]
+dev = [
+    "ruff==0.8.3"
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"

__tests__/fixtures/pyproject-dependency-dev-project/src/pyproject_dependency_dev_project/__init__.py

@@ -0,0 +1,2 @@
+def hello() -> str:
+    return "Hello from python-project!"

__tests__/fixtures/pyproject-dependency-dev-project/src/pyproject_dependency_dev_project/hello_world.py

@@ -0,0 +1 @@
+print("Hello world!")

__tests__/fixtures/python-project/pyproject.toml

@@ -5,7 +5,7 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.12"
 dependencies = [
-    "ruff>=0.6.2",
+    "ruff==0.6.2",
 ]
 
 [build-system]