[Feature request]: Add Startup Brigness for IKEA tradfri LED2005R5/LED2106R3

[dannyneup]

Is your feature request related to a problem? Please describe

I need to be able to set different startup brightnesses for different bulbs. For now I can only set a default color temp. The brightness defaults to 100%.

Describe the solution you'd like

I would like to have a exposed value to set the startup brightness just like with the "color temp startup".

Describe alternatives you've considered

I've tested aha with these devices. I have tried these devices with zha. Zha offers this functionality. worked great. I don't want to switch to zha just because of this device.

Additional context

[github-actions]

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