Updated Static filter syntax (markdown)

Static-filter-syntax.md

@@ -203,6 +203,7 @@ uBO extends ABP filter syntax.
 - [$redirect](#redirect)
 - [$redirect-rule](#redirect-rule)
 - [$removeparam](#removeparam)
+- [$replace](#replace)
 
 ## Static network filtering
 
@@ -901,6 +902,10 @@ Cosmetically added params cannot be removed via `removeparam` (see related comme
 
 See also: [Filter Performance](./Filter-Performance#removeparam-modifier)
 
+#### `replace`
+
+See <https://adguard.com/kb/general/ad-filtering/create-own-filters/#replace-modifier>
+
 ***
 
 ## Static extended filtering