Revert "Revert "jekyll-lunr-js-search added""

This reverts commit 127b8972137b315876f7fd77c92cd78a95ae21cf.
Revert "Revert "Revert "jekyll-lunr-js-search added"""

This reverts commit 579c6fe2b4e5b957b8c12d0f930819b3d1727cda.
search added