patch 9.1.0592: runtime: filetype: Mediawiki files are not recognized

Problem:  filetype: Mediawiki files are not recognized
Solution: detect "*.mw" and "*.wiki" as mediawiki filetype,
          include basic syntax and filetype plugins.
          (AvidSeeker)

closes: #15266

Signed-off-by: AvidSeeker <avidseeker7@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/filetype.vim

@@ -810,10 +810,6 @@ au BufNewFile,BufRead *.fish			setf fish
 " Flatpak config
 au BufNewFile,BufRead */flatpak/repo/config	setf dosini
 
-" FlexWiki - disabled, because it has side effects when a .wiki file
-" is not actually FlexWiki
-"au BufNewFile,BufRead *.wiki			setf flexwiki
-
 " Focus Executable
 au BufNewFile,BufRead *.fex,*.focexec		setf focexec
 
@@ -1430,6 +1426,9 @@ au BufNewFile,BufRead .mbsyncrc			setf conf
 " mcmeta
 au BufNewFile,BufRead *.mcmeta			setf json
 
+" MediaWiki
+au BufNewFile,BufRead *.mw,*.wiki		setf mediawiki
+
 " Mercurial (hg) commit file
 au BufNewFile,BufRead hg-editor-*.txt		setf hgcommit
 
@@ -2419,7 +2418,7 @@ au BufNewFile,BufRead *.tcl,*.tm,*.tk,*.itcl,*.itk,*.jacl,.tclshrc,.wishrc,.tcls
 " Xilinx's xsct and xsdb use tcl
 au BufNewFile,BufRead .xsctcmdhistory,.xsdbcmdhistory	setf tcl
 
-" templ 
+" templ
 au BufNewFile,BufRead *.templ			setf templ
 
 " Teal