fix search

[obriencj]

Elegant defaulted to expecting the tipue-search plugin was enabled. However, this is a deprecated and unmaintained plugin.
https://github.com/pelican-plugins/tipue-search

There is a replacement plugin, using a different backend, which will take some adaptation to use
https://github.com/pelican-plugins/search

it requires a new binary to be installed into the container, which looks to not be a default part of ubuntu.

for now I am going to add a switch to disable the search field if no SEARCH_URL was explicitly set, and will remove the default value of "search.html" from the template itself.

[obriencj]

stork is the search indexer backend for pelican-search

stork development has halted
jameslittle230/stork#360

pelican-search thread on this problem
pelican-plugins/search#35