Added pyproject.toml with project metadata and dev dependencies (#22)

### Changes included

####  Added pyproject.toml with:
- Project name, version, author, and Python version
- Runtime dependency: openmm>=8.3.0
- Development dependencies: black, ruff
- Prepared for setuptools-based build backend

Author: siddharth7113

pyproject.toml

@@ -0,0 +1,24 @@
+[build-system]
+requires = ["setuptools>=61.0", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "pyaptamer"
+version = "0.0.1.dev0"
+description = "Python library for aptamer simulation"
+readme = "README.md"
+requires-python = ">=3.10"
+authors = [
+    { name="Your Name", email="your@email.com" }
+]
+
+dependencies = [
+    "openmm>=8.3.0,<8.4.0"
+]
+
+[project.optional-dependencies]
+dev = [
+    "ruff>=0.12.0",
+    "black>=25.0",
+    "pytest>=8.0.0"
+]