Ignoring the children of manifest assets when using cspAssetRegex

[AnujRNair]

Summary

Currently, if you pull in the manifest asset, it's children are defined as all of the other assets in the build.
This causes the plugin to hash all assets in the build, rather than only the smaller subset that the developer has defined using the cspAssetRegex option.

This change ignores the children of the manifest asset when recursively iterating through the assets to hash

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've written tests to cover the new code and functionality included in this PR.
• I've read, agree to, and signed the Contributor License Agreement (CLA).

[codecov-io]

Codecov Report

Merging #4 into master will decrease coverage by 0.59%.
The diff coverage is 80%.

@@ Coverage Diff @@ ## master #4 +/- ## ======================================== - Coverage 96.4% 95.8% -0.6%  ======================================== Files 2 2 Lines 139 143 +4 Branches 17 19 +2 ======================================== + Hits 134 137 +3  - Misses 5 6 +1

Impacted Files	Coverage Δ
plugin.js	94.25% <80%> (-0.93%)	⬇️

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[rowanoulton]

It'd be great if there were a more official way of detecting this.

[AnujRNair]

Agreed - Looking through CommonsChunkPlugin and webpack-manifest-plugin, I can't see a good way to detect that the chunk is the manifest chunk. If this becomes problematic, I will certainly look for a better way to detect this

[rowanoulton]

LGTM