Reader without consumer group read at last offset

[zekth]

Describe the solution you would like

Currently the implementation when spinning a consumer without consumer group will always start at the first offset:

kafka-go/reader.go

Line 707 in a558bb8

offset: FirstOffset,

Would it be possible to support the StartOffset parameter instead?

The goal in here is to spin a consumer without a consumer group idea to get only the latest offsets