Add dependencies via Composer

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Related issues: #13 Dependencies (non-exhaustive):

• https://github.com/harvesthq/chosen
• https://github.com/crowdfavorite/jquery.hotkeys
• https://github.com/crowdfavorite/linkify
• https://github.com/crowdfavorite/sidr
• https://github.com/crowdfavorite/jquery-scrollintoview
• https://github.com/crowdfavorite/JSON-js
• https://github.com/crowdfavorite/twitter-text-js
• https://github.com/crowdfavorite/php-markdown-extra-extended
• https://github.com/crowdfavorite/phpjs
• https://github.com/ajaxorg/ace CF-built dependencies:
• https://github.com/crowdfavorite/wp-taxonomy-filter
• https://github.com/crowdfavorite/wp-gatekeeper