Add root property to Document and Editor (#17)

Provides doc.root as a convenient alternative to doc[()].
Returns the entire document parsed as a Python object.

Author: nathanjmcdougall

README.md

@@ -56,6 +56,7 @@ modified.
 ```python
 doc = yamltrip.loads("items:\n  - a\n  - b")
 
+doc.root                      # {"items": ["a", "b"]}
 doc["items"]                  # ["a", "b"]
 doc["items", 0]               # "a"
 ("items", 0) in doc           # True

src/yamltrip/document.py

@@ -93,6 +93,11 @@ def source(self) -> str:
         """The current YAML source text."""
         return self._source
 
+    @property
+    def root(self) -> Any:
+        """The entire document parsed as a Python object."""
+        return self[()]
+
     def __eq__(self, other: object) -> bool:
         """Compare documents by their source text."""
         if not isinstance(other, Document):

src/yamltrip/editor.py

@@ -83,6 +83,11 @@ def document(self) -> Document:
             raise RuntimeError(msg)
         return self._document
 
+    @property
+    def root(self) -> Any:
+        """The entire document parsed as a Python object."""
+        return self.document.root
+
     def __getitem__(self, keys: object) -> Any:
         """Retrieve the parsed value at the given path."""
         return self.document[keys]