deprecate manatee.json; add 2020-12 support for json-everything

Author: gregsdennis

_data/validator-libraries-modern.yml

@@ -8,14 +8,9 @@
       license: "AGPL-3.0-only"
     - name: JsonSchema.Net
       url: https://github.com/gregsdennis/json-everything
-      date-draft: [2019-09]
+      date-draft: [2019-09, 2012-12]
       draft: [7, 6]
       license: MIT
-    - name: Manatee.Json
-      url: https://github.com/gregsdennis/Manatee.Json
-      date-draft: [2019-09]
-      draft: [7, 6, 4]
-      license: MIT
 - name: C
   implementations:
     - name: WJElement

_data/validator-libraries-obsolete.yml

@@ -6,6 +6,11 @@
       notes:
       draft: [4]
       license: Ms-PL
+    - name: Manatee.Json
+      url: https://github.com/gregsdennis/Manatee.Json
+      date-draft: [2019-09]
+      draft: [7, 6, 4]
+      license: MIT
 - name: C++
   anchor-name: cpp
   implementations: