luci-mod-dsl: Manually add one language to trigger weblate

Weblate needs at least one language .po file to exist for it
to notice the new component. Just the .pot template is not enough.

Add Spanish manually.

This fixes commit 977c9ac6

 that only added the template.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>