Preferred JS package manager per Gaëtan Burg

Preferred JS package manager is a web extension that all install commands on `npmjs.com`, `classic.yarnpkg.com` and `yarnpkg.com` package pages with the one of your preferred package manager ( npm, pnpm, yarn ).

Other features are available :
- Readme code blocks with install instructions are modified too with the possibility to display the original content.
- A copy button on all Readme code blocks
- Context menus are added to allow a quick search of a selected text on `npmjs.com` and `yarnpkg.com`

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Source Code :
https://gitlab.com/tag9724/preferred-js-package-manager