Bump image_optim from 0.26.5 to 0.28.0

Bumps image_optim from 0.26.5 to 0.28.0.

Changelog

Sourced from image_optim's changelog.

v0.28.0 (2020-12-18)

• Fix and update list of markers in jpegoptim worker: allow to pass com instead of incorrect comments and add missing xmp and none #188 @​toy
• Add --skip-if-larger flag to pngquant worker. The pngquant worker already does this, but this will make it fail faster. #125 #181 @​iggant @​oblakeerickson
• Add method option for jpegrecompress, default to ssim #102 #103 #182 @​ramiroaraujo @​oblakeerickson

v0.27.1 (2020-09-30)

• Fixed atomic replacement for case when equal File::Stat#dev doesn't mean that file can be linked #180 @​toy

v0.27.0 (2020-08-27)

• Use .tmp as the extension for temporary file if it needs to be created for atomic replacement #178 @​toy
• Don't create a temporary file in destination directory for atomic replacement if temporary directory is on same device as destination #178 @​toy

Commits

• 6803161 v0.28.0
• b9bcf23 fix links in changelog entries
• a3e177a fix and update jpegoptim list of markers, resolves #188
• 672bb3c travis: remove ruby 1.8
• d820429 rubocop 1.4.2
• 7286c6c rubocop 1.3.1
• 118f2e8 Merge pull request #182 from oblakeerickson/compression-methods-for-jpeg-comp...
• 4e2c9e8 Update with pr feedback
• d069aa7 Add method option to jpeg-recompress for passing in comparison metrics
• eaf28a9 rubocop 1.1.0
• Additional commits viewable in compare view