Add initial implementation of Matrix chat widget with Flask blueprint

- Create .gitignore to exclude Python-related files
- Implement chat blueprint in __init__.py
- Add chat HTML template with input and message display
- Create CSS for chat styling
- Develop JavaScript for chat functionality and Matrix API integration
- Configure pyproject.toml for project metadata and dependencies

pyproject.toml

@@ -0,0 +1,17 @@
+[build-system]
+requires = ["setuptools>=61"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "matrix-iframe"
+version = "0.1.0"
+description = "Embeddable Matrix room chat widget as a Flask blueprint"
+requires-python = ">=3.9"
+dependencies = ["flask>=2.0"]
+
+[tool.setuptools.packages.find]
+where = ["."]
+include = ["matrix_iframe*"]
+
+[tool.setuptools.package-data]
+matrix_iframe = ["templates/**/*", "static/**/*"]