[IMPROVEMENT] Add serialize to dict & deserialize from dict option

[Thijss]

Both me and @AllianderTim would like to add this feature.

The current serialize method on the Grid only serializes to json, but for some applications it can be useful to serialize to a variable (e.g. dict) instead. Shouldn't be too hard to implement because we are basically already working with dicts when writing to/reading from json.

Suggested method signature change:

class Grid:
    ...
    def serialize(path: Path, mode: Literal["json", "dict"] = "json", **kwargs):
        ...

We could then use @overload to specify different output types, depending on the mode.
We did a similar thing for FancyArray.__getitem__

[vincentkoppen]

@jaapschoutenalliander already has a draft PR open: #219.
I would say that an additional mode for the serialize looks good to me, the deserialize is a bit tricky. It now only has a path argument, maybe we want to add a data argument? And then you supply one of the two.
Or a seperate method?

def deserialize(cls: type[Self], path: Path) -> Self:

--> (?)

def deserialize(cls: type[Self], path: Path, data: dict) -> Self: