* disable NewCops

* update TargetRubyVersion

* Fix Lint/MissingSuper for ActiveModelSerializers::Model

* Fix Lint/MissingSuper for feed

* Fix Lint/FloatComparison

* Do not use instance variables

* Bump rubocop from 0.86.0 to 0.88.0

Bumps [rubocop](https://github.com/rubocop-hq/rubocop) from 0.86.0 to 0.88.0.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop/compare/v0.86.0...v0.88.0)

Signed-off-by: dependabot[bot] <support@github.com>

* Fix for latest RuboCop

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

* Fix contrast calculation for thumbnail color extraction

Luminance calculation was using 0-255 RGB values instead of 0-1 sRGB values,
leading to incorrectly-computed contrast values.

Since we use ColorDiff already, just use its XYZ colorspace conversion code
to get the value.

* Require at least 3:1 contrast for both accent and foreground colors

* Lower required contrast for the accent color