jekyll-plugin-include

https://github.com/decipher-media/jekyll-plugin-include

A Jekyll liquid tag plugin which allows includes directly from plugins' `_include` directories, with optional ability to override with files present in site includes_dir (if they exist). Normally, Jekyll's `include` tag can only search for files in the site's single configured includes directory (and that of the *theme* plugin, if it using one). That means that if a plugin wants to provide you with a template/fragment via includes, the best it can do is ask you to copy it into your own repo manually. This plugin then makes it easy to use includes that ship *with* a plugin directly *from* a plugin. And if a modified version of the file is provided in the site's own includes directory, it can intelligently use that one instead! And for plugin developers, this provides a way to ship and use includes without leaning on the user to manage the unmodified files themselves.