Be less restrictive for language part of URL

People might use different strings here, so let's not be strict about
language name format and allow anything.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/urls.py

@@ -32,7 +32,7 @@ from weblate.sitemaps import SITEMAPS
 import weblate.accounts.urls
 
 # URL regexp for language code
-LANGUAGE = r'(?P<lang>[^/-]{2,3}([_-][A-Za-z]{2})?(@[a-z]+)?)'
+LANGUAGE = r'(?P<lang>[^/]+)'
 
 # URL regexp for project
 PROJECT = r'(?P<project>[^/]+)/'