feat: add atuin shell history integration for Fish

Initialize atuin in Fish shell for synced fuzzy history search with CTRL+R.

home/.chezmoitemplates/scripts/commonrc.fish.tmpl

@@ -116,3 +116,8 @@ function wt
     end
 end
 {{- end }}
+
+# atuin (magical shell history)
+if command -q atuin
+    atuin init fish | source
+end