blockquote support, /closes #25

example.html

@@ -8,4 +8,5 @@ <h3>Lists and formatting are supported</h3>
 </ol>
 <hr />
 <h3>Other features</h3>
+<Blockquote>This is block quote</Blockquote>
 <p>This is paragraph!</p><p>And one more with <q>quote</q>.</p>

src/sulguk/entities/decoration.py

@@ -76,14 +76,13 @@ def render(self, state: State) -> None:
 
 
 @dataclass
-class Blockquote(Group):
-    block: bool = True
+class Blockquote(DecoratedEntity):
+    language: Optional[str] = None
 
-    def render(self, state: State) -> None:
-        indent = state.canvas.indent
-        state.canvas.indent += 1
-        super().render(state)
-        state.canvas.indent = indent
+    def _get_entity(self, offset: int, length: int) -> MessageEntity:
+        return MessageEntity(
+            type="blockquote", offset=offset, length=length,
+        )
 
 
 @dataclass