[enh] Add french translation for webapp.

searx/translations/fr/LC_MESSAGES/messages.po

 
 #: searx/webapp.py:167
 msgid "{minutes} minute(s) ago"
-msgstr ""
+msgstr "Il y a {minutes} minute(s)"
 
 #: searx/webapp.py:169
 msgid "{hours} hour(s), {minutes} minute(s) ago"
-msgstr ""
+msgstr "Il y a {hours} heure(s), {minutes} minute(s)"
 
 #: searx/engines/__init__.py:311
 msgid "Page loads (sec)"