[palette_generator] An error in calculating titleTextColor and bodyTextColor for PaletteColor #31592

First, I'm not very familiar with color theory so I might be wrong...

But I highly doubt that palette_generator is calculating titleTextColor and bodyTextColor for PaletteColor incorrectly.

As an example, in the test 'PaletteGenerator finds dominant color and text colors'.

Dominant color is 0xff0000ff while titleTextColor is 0xbc000000 and bodyTextColor is 0xda000000

The contrast ratio between text color and dominant color is extremely low, which doesn't seem correct.
https://contrast-ratio.com/#hsla%280%2C0%25%2C0%25%2C0.85%29-on-%230000ff

I think the problem is palette_generator converts Color to HSLColor then directly uses lightness in HSLColor. However it seems like relative luminance is different from lightness in HSLColor.

See line 687, 688 here
https://github.com/flutter/packages/blob/e40537243c1e07cbf47e1ffefc947c4092e34c28/packages/palette_generator/lib/palette_generator.dart#L687

Since it seems to be a easy fix I submitted a pr here :P
flutter/packages#18