Allow to write to unexisting directory

`ifcopenshell.write("/unexisting/path/model.ifc")` was failing without
throwing an error. It now works and a test ensure it works.

src/ifcopenshell-python/ifcopenshell/file.py

@@ -462,6 +462,7 @@ class file(object):
         >>> model.write("path/to/model.anyextension", format=".ifcXML")
         """
         path = Path(path)
+        path.parent.mkdir(parents=True, exist_ok=True)
         if format == None:
             format = ifcopenshell.util.file.guess_format(path)
         if format == ".ifcXML":

src/ifcopenshell-python/test/test_write.py

@@ -61,3 +61,6 @@ class TestWrite:
 
     def test_write_anyextension_ifczip_ifcxml_format(self):
         self.assert_model_is_written("model.anyextension", format=".ifcXML", zipped=True)
+
+    def test_write_to_non_existing_dir(self):
+        self.assert_model_is_written("tmp/model.ifczip")