docs: add v6.4.0 and v6.3.0 to docs (#2472)

add v6.4.0 and v6.3.0 to docs

Author: mpoke

docs/supported_versions.json

@@ -1,4 +1,6 @@
 [
+    "v6.4.0",
+    "v6.3.0",
     "v6.1.0",
     "v5.2.0",
     "v4.5.0"