Update changelog

Author: sqrrrl

CHANGELOG.md

@@ -5,7 +5,8 @@
 * Support local image upload (via file.io) and rasterization of SVG and TeX/MathML expressions
 * Fix image alignment when included in a column
 * Allow offsets for images
-* Allow custom layouts via markdown
+* Allow custom layouts via markdown, copying from existing template. Note
+  this changes the drive scope and requires reauthorization.
 * Update dependencies
 * Migrate code to TypeScript