Update license format and add setuptools packages

pyproject.toml

@@ -3,7 +3,7 @@ name = "gamdl"
 version = "2.8.3"
 description = "A command-line app for downloading Apple Music songs, music videos and post videos."
 readme = "README.md"
-license = { text = "MIT" }
+license = "MIT"
 requires-python = ">=3.10"
 dependencies = [
     "async-lru>=2.0.5",
@@ -24,3 +24,6 @@ Repository = "https://github.com/glomatico/gamdl"
 
 [project.scripts]
 gamdl = "gamdl.cli.cli:main"
+
+[tool.setuptools]
+packages = ["gamdl"]