Todo

• [x] Adding a property to an existing class:
  • [x] Add the "object id" as a primitive type: https://github.com/realm/realm-studio/blob/master/src/ui/RealmBrowser/primitives.ts#L19, which enables it to be selected when adding a property to a Realm file.
• [x] Creating an object:
  • [x] Add a new component to the collection of controls when creating an object.
  • [x] Update `generateInitialValue` to generate an appropriate initial value.
  • [x] Update the `TypeControl` component to display the new control component.
• [x] Showing values in the table:
  • [x] Add a new component to the collection of cell type components or reuse the StringCell component.
  • [x] Add a case for "object id" in the `Cell` component, to show the new component.
  • [x] Update `parsers` to parse from string to a BSON ObjectId.
• [x] Update the `AddClassModal` to include the "object id" as primary key type (defaulting to the _id property name).
• [ ] Update the schema exporter and its tests.