Add Láadan (ldn)

Requested at
https://translatewiki.net/w/i.php?title=Support&oldid=11429494

With contstructed languages, there are sometimes potential issues
of copyright, but in this case, it seems OK. Looking at the website:

Is it possible to get permission to do things with Láadan?
What if I want to write poetry in Láadan, for example, or fiction?
What if I want to start a Láadan study group?
What if I want to make some changes in the language?

Answer: No living human language is “owned” by anyone or anything.
Since Láadan was launched as a scientific experiment, intended
to live or die on its own like any other language, there was
no way I could “own” it except in the sense of having copyrighted
its original form. From the very beginning, every chance I got,
I made it clear that I not only was willing to have other people
do things with the language, I encouraged it. Nobody has to have
my permission; nobody has to clear what they do with me,
or report to me, or anything like that.

from: https://laadanlanguage.com/articles/articles-by-suzette/laadan-faq/

data/language-data.json

@@ -2375,6 +2375,13 @@
             ],
             "лакку"
         ],
+        "ldn": [
+            "Latn",
+            [
+                "WW"
+            ],
+            "Láadan"
+        ],
         "lez": [
             "Cyrl",
             [