Modify webpack-stats-diff-action with some more granular functionality

[rsheldiii]

Whoops, meant to make this on my own fork. I'd be happy to merge these changes which mostly center around displaying a breakdown of percentages changed file-by-file, but they are a bit opinionated, so I understand if they aren't ideal. I'm planning on merging these changes on my fork and offering that as an alternative action, though I wish GHA would allow for private actions already