V3 - Do not throw exception for non-required chunks.

[JimBobSquarePants]

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Description

Fixes #2925

[Copilot]

Pull Request Overview

This PR ensures that non-required WebP chunks don’t trigger an exception by making chunk-size reads optional and adds a test case for Issue 2925.

• Added a new test image and test to verify decoding of non-required chunks (Issue 2925).
• Updated ReadChunkSize to accept a required flag and skip unknown chunks without throwing.
• Registered the new test image in TestImages.cs.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/Images/Input/Webp/issues/Issue2925.webp	Added test fixture for Issue 2925
tests/ImageSharp.Tests/TestImages.cs	Registered Issue2925 constant
tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs	Added WebpDecoder_CanDecode_Issue2925 test
src/ImageSharp/Formats/Webp/WebpDecoderCore.cs	Made ReadChunkSize optional for non-required chunks

Comments suppressed due to low confidence (1)

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs:516

• [nitpick] The exception message is generic; consider specifying that the failure occurred while reading the chunk size (e.g., "Invalid WebP data: unable to read chunk size.") to improve clarity.

throw new ImageFormatException("Invalid Webp data.");