Implement adding new translation for JSON

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/formats.py

@@ -863,6 +863,21 @@ class JSONFormat(FileFormat):
     format_id = 'json'
     loader = ('jsonl10n', 'JsonFile')
 
+    @classmethod
+    def supports_new_language(cls):
+        '''
+        Checks whether we can create new language file.
+        '''
+        return True
+
+    @staticmethod
+    def add_language(filename, code, base):
+        '''
+        Adds new language file.
+        '''
+        with open(filename, 'w') as output:
+            output.write('{}\n')
+
 
 FILE_FORMAT_CHOICES = [
     (fmt, FILE_FORMATS[fmt].name) for fmt in sorted(FILE_FORMATS)