Add SQLite docs on collations/case-insensitivity

For collations and case sensitivity, we have [these docs](https://docs.microsoft.com/en-us/dotnet/standard/data/sqlite/collation#custom-collation) for Microsoft.Data.SQLite. These docs show how to use the COLLATE operator, but not creating a column with a collation (which I think is the preferred way to do things, allowing index usage?).

Apart from that, we may want to have a section in the EF Core SQLite provider docs, guiding people specifically how to do case-insensitivity (see e.g. https://github.com/dotnet/efcore/issues/8033#issuecomment-1110757159).