Invoices are in french

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

apps/treasury/templates/treasury/invoice_sample.tex

-{% load escape_tex %}
+{% load escape_tex i18n %}
+{% language fr %}
 \documentclass[a4paper,11pt]{article}
 
 \usepackage{fontspec}
@@ -176,3 +177,4 @@ TVA non applicable, article 293 B du CGI.
 \end{center}
 
 \end{document}
+{% endlanguage %}