also mark IS DISTINCT FROM as supported

This seems to really be just an alias for IS:

"The IS NOT DISTINCT FROM operator is an alternative spelling for the IS
operator. Likewise, the IS DISTINCT FROM operator means the same thing
as IS NOT. Standard SQL does not support the compact IS and IS NOT
notation. Those compact forms are an SQLite extension. You have to use
the prolix and much less readable IS NOT DISTINCT FROM and IS DISTINCT
FROM operators on other SQL database engines."

COMPAT.md

@@ -187,7 +187,7 @@ Feature support of [sqlite expr syntax](https://www.sqlite.org/lang_expr.html).
 | (NOT) REGEXP              | No      |                                          |
 | (NOT) MATCH               | No      |                                          |
 | IS (NOT)                  | Yes     |                                          |
-| IS (NOT) DISTINCT FROM    | No      |                                          |
+| IS (NOT) DISTINCT FROM    | Yes     |                                          |
 | (NOT) BETWEEN ... AND ... | No      |                                          |
 | (NOT) IN (subquery)       | No      |                                          |
 | (NOT) EXISTS (subquery)   | No      |                                          |