Introduce OptionalPrefixToken and OptionalPostfixToken

Add typedefs for OptionalPrefixToken and OptionalPostfixToken.

Author: Bashamega

inputfiles/patches/html-autocomplete.kdl

@@ -72,3 +72,11 @@ enum AutoFillContactField {
 enum AutoFillCredentialField {
   webauthn
 }
+
+typedef OptionalPrefixToken overrideType=#"`${T} ` | """# {
+    typeParameters T extends=string
+}
+
+typedef OptionalPostfixToken overrideType=#"` ${T}` | """# {
+    typeParameters T extends=string
+}