[fix] doc - add missing quotation marks in docs/build-templates

Escape the all the quotation marks (" --> \") in docs/build-templates.

The scripts are *bash evaluated* (e.g)::

  eval "echo \"$(< "${REPO_ROOT}/docs/build-templates/searx.rst")\""

Backslash, quotation marks and other need to be escaped.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>