Accept "pos" as an alias for ctag and default certainty to 1 for TreeTagger

Fixes CoNLL-U-Treetagger compatibility.

Change-Id: I6301b3d826da8330ee33d83a286f765b08af04b6
diff --git a/Changes b/Changes
index 338a5d5..aac2050 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,9 @@
 0.53 2023-03-20
         - Added Spacy support. (kupietz)
+        - Support 'pos' as an alternative to 'ctag'
+          in Treetagger. (kupietz)
+        - Change default certainty value in TreeTagger
+          to 1.
 
 0.52 2023-01-23
         - Introduced 'quiet' flag.