docs: update readme tested up to 6.5 of wp

Author: danhthong

readme.txt

@@ -3,8 +3,8 @@ Contributors:      ellatrix, wordpressdotorg, isvictorious, danhthong, alilyons
 Tags:              presentations, slides, powerpoint, keynote, gutenberg, blocks
 Requires at least: 5.3
 Requires PHP:      5.6
-Tested up to:      6.0
-Stable tag:        1.0.3
+Tested up to:      6.5
+Stable tag:        1.0.4
 License:           GPLv2 or later
 License URI:       https://www.gnu.org/licenses/gpl-2.0.html