Added poetry integration.

Description:
* Fixed github actions;
* Removed requirements.txt;
* Fixed CONTRIBUTING.md;
* Fixed black and flake8.

Signed-off-by: Pavel <win10@list.ru>

ormar/relations/utils.py

@@ -8,7 +8,7 @@ if TYPE_CHECKING:  # pragma no cover
 
 
 def get_relations_sides_and_names(
-    to_field: ForeignKeyField, parent: "Model", child: "Model",
+    to_field: ForeignKeyField, parent: "Model", child: "Model"
 ) -> Tuple["Model", "Model", str, str]:
     """
     Determines the names of child and parent relations names, as well as