Update dependency pngjs to v7

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
pngjs (source)	^5.0.0 -> ^7.0.0

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Release Notes

pngjs/pngjs (pngjs)

v7.0.0

• BREAKING - Drop support for node 12 (Though nothing incompatible in this release yet)
• Switch to a pngjs organisation

v6.0.0

• BREAKING - Sync version now throws if there is unexpected content at the end of the stream.
• BREAKING - Drop support for node 10 (Though nothing incompatible in this release yet)
• Reduce the number of files included in the package

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Configuration

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