feat: add support for .pkg and .dmg files

[DanielMcAssey]

Alternative to #154 that specifically targets dmg and pkg files.

Created this from comment on #152.

This is currently broken with change #152, as codesign doesn't seem to like reading .pkg

[continuous-auth[bot]]

:tada: This PR is included in version 2.3.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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