WIP: `copy-file` to work with markdown #1974

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closes #1223

has a regression, and two bugs. will load onNavigate twice. used to not copy everything (now nothing at all): not everything: https://github.com/sindresorhus/refined-github/blob/master/contributing.md supposedly everything: https://github.com/sindresorhus/refined-github/blob/master/readme.md