[v4] Allow indexing lists

[CaptainDario]

Is your feature request related to a problem? Please describe.
Isar v3 allowed indexing lists which was important to me because performance could be dramatically increased by using it.

However, when I try using a List that has an index in v4 I encounter

List properties cannot be indexed
package:database_builder/src/tatoeba_to_isar/data_classes.dart:43:16
   ╷
43 │   List<String> mecabBaseForms;
   │                ^^^^^^^^^^^^^^
   │

Describe the solution you'd like
Allow indexing lists in v4

Describe alternatives you've considered
Do not use indexes for lists.
However, before migrating my whole code base I would like to know if this has severe impacts on performance?

Version

• Isar v4