Update documentation

layouts/partials/site-last-mod.html

@@ -1,10 +1,20 @@
-{{- /* The .Site.LastChange was deprecated in Hugo v0.123.0 */ -}}
-{{- /* Use .Site.Lastmod if .Site.Hugo.Version greater than or equal to v0.123.0 */ -}}
-{{- /* Otherwise, use .Site.LastChange */ -}}
+{{- /*
 
-{{- /* For more see: https://github.com/gohugoio/hugo/releases/tag/v0.123.0 */ -}}
+This partial is used to get the last modification date of the site.
 
-{{- /* Usage: {{ $siteLastMod := partial "site-last-mod.html" . }} */ -}}
+In Hugo v0.123.0, the .Site.LastChange variable was deprecated in favour of .Site.Lastmod.
+To maintain compatibility with older versions of Hugo, this partial checks the Hugo version.
+If the version is greater than or equal to v0.123.0, it uses .Site.Lastmod.
+Otherwise, it falls back to using .Site.LastChange.
+
+The result is stored in the $siteLastMod variable and returned by the partial.
+
+Usage:
+
+    {{ $siteLastMod := partial "site-last-mod.html" . }}
+
+For more information, see: https://github.com/gohugoio/hugo/releases/tag/v0.123.0
+*/ -}}
 
 {{- $siteLastMod := "" -}}