feat: Initial oneshot command proposal

tests/test_oneshot.py

@@ -0,0 +1,12 @@
+from .fixtures import *
+
+def test_oneshot_command_exists(tmp_path):
+    os.chdir(tmp_path)
+    process = subprocess.run(['archivebox', 'oneshot'], capture_output=True)
+    assert not "invalid choice: 'oneshot'" in process.stderr.decode("utf-8")
+
+def test_oneshot_commad_saves_page_in_right_folder(tmp_path):
+    process = subprocess.run(["archivebox", "oneshot", f"--out-dir={tmp_path}", "http://127.0.0.1:8080/static/example.com.html"], capture_output=True)
+    items = ' '.join([str(x) for x in tmp_path.iterdir()])
+    assert "index.json" in items
+