Add link def to CHANGELOG and clean up whitespace

[chalin]

• Followup to [feat] Add base support of td-content-after-header hook #2192

$ (cd user*/public && g diff -bw) | grep ^diff | head
diff --git a/project/changelog/index.html b/project/changelog/index.html
diff --git a/refcache.json b/refcache.json
diff --git a/sitemap.xml b/sitemap.xml