Document changes in manpage

Add section on rewrite rules and extend example

man/waybar-sway-window.5.scd

@@ -66,12 +66,32 @@ Addressed by *sway/window*
 	default: true ++
 	Option to disable tooltip on hover.
 
+*rewrite*: ++
+	typeof: object ++
+	Rules to rewrite window title. See *rewrite rules*.
+
+# REWRITE RULES
+
+*rewrite* is an object where keys are regular expressions and values are
+rewrite rules if the expression matches. Rules may contain references to
+captures of the expression.
+
+Regular expression and replacement follow ECMA-script rules.
+
+If no expression matches, the title is left unchanged.
+
+Invalid expressions (e.g., mismatched parentheses) are skipped.
+
 # EXAMPLES
 
 ```
 "sway/window": {
     "format": "{}",
-    "max-length": 50
+    "max-length": 50,
+    "rewrite": {
+      "(.*) - Mozilla Firefox": "🌎 $1",
+      "(.*) - zsh": "> [$1]"
+    }
 }
 ```