Update dependency promise-readable to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
promise-readable	devDependencies	major	^5.0.3 -> ^6.0.0

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Release Notes

dex4er/js-promise-readable

v6.0.0

Compare Source

• Requires Node >= 10.
• Converted from tslint to eslint.
• Uses @​types/node v14

v5.0.4

Compare Source

• Chunk might be an empty string: fixes #​32.

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[coveralls]

Coverage remained the same at 90.621% when pulling a72f14a on renovate/promise-readable-6.x into ab8b85d on master.