feat(image_processing): Add types for v2.2

[ksss]

Adds RBS for image_processing, which doesn't ship its own sig/ directory.

Signatures are written against image_processing 2.2.0 and cover the major public API:

• ImageProcessing::Chainable: source, convert, loader, saver, instrumenter, apply, operation, call, branch
• Built-in macros shared by both processors, plus their bang (!) variants: resize_to_limit, resize_to_fit, resize_to_fill, resize_and_pad, resize_to_cover, crop, rotate, composite
• ImageProcessing::Vips / ImageProcessing::MiniMagick (both extend Chainable) and their Processor classes
• Builder, Pipeline, Processor, Error

🤖 Generated with Claude Code

[github-actions]

@ksss Thanks for your contribution!

Please follow the instructions below for each change.
See also: https://github.com/ruby/gem_rbs_collection/blob/main/docs/CONTRIBUTING.md

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image_processing

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[ksss]

/merge