Is your feature request related to a problem? Please describe.
It could be considered a bug that glow berries (which are light source blocks) are not used by LambDynamicLights

Describe the solution you'd like
Glow berries should function as dynamic light when in the player's (off)hand or in item entity form

Describe alternatives you've considered
I would like to know if this is possible with a resource pack or datapack for the time being until it is implemented in the mod.

Additional context

Will be added in the next update, in the meantime this can be fixed via a resource pack with the path assets/<namespace>/dynamiclights/item/glow_berries.json
and with content:

{
  "item": "minecraft:blaze_rod",
  "luminance": 14
}