Migrate ForensicsWiki links to the new forensics.wiki domain

See kaitai-io/kaitai_struct#1066

Author: generalmimon

user_guide.adoc

@@ -1659,7 +1659,7 @@ key-value pairs, e.g.:
 ----
 meta:
   xref:
-    forensicswiki: Portable_Network_Graphics_(PNG)
+    forensicswiki: portable_network_graphics_(png)
     iso: '15948:2004'
     justsolve: PNG
     loc: fdd000153
@@ -1676,10 +1676,15 @@ There are several "well-known" keys used by convention by many spec
 authors to provide good cross references of their formats:
 
 * `forensicswiki` specifies an article name at
-  https://forensicswiki.xyz/page/Main_Page[Forensics Wiki], which is a
+  https://forensics.wiki/[Forensics Wiki], which is a
   CC-BY-SA-licensed wiki with information on digital forensics, file
   formats and tools. A full link could be generated as
-  `https://forensicswiki.xyz/page/` + this value.
+  `+https://forensics.wiki/+` + this value + `/`.
++
+For consistency, insert parentheses in this value literally (without
+using percent-encoding) - e.g. use `extended_file_system_(ext)` instead
+of `extended_file_system_%28ext%29`.
+
 * `iso` specifies an ISO/IEC standard number, a reference to a standard
   accepted and published by https://www.iso.org/[ISO] (International
   Organization for Standardization). Typically these standards are not