patch 9.1.1647: filetype: Cangjie files are not recognized

Problem:  filetype: Cangjie files are not recognized
Solution: Detect *.cj files as cangjie filetype, include a syntax plugin
          (WuJunkai2004)

This commit introduces a new syntax highlighting file for the Cangjie
programming language, includes 4 parts as required:
- The main syntax file: runtime/syntax/cangjie.vim
- The filetype detection rule in: runtime/filetype.vim
- The documentation update in: runtime/doc/syntax.txt
- Some menus

References:
- https://gitcode.com/Cangjie
- https://cangjie-lang.cn/

fixes: 18014
closes: #18027

Signed-off-by: WuJunkai2004 <wujunkai20041123@outlook.com>
Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -156,6 +156,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     cabalproject: ['cabal.project', 'cabal.project.local'],
     cairo: ['file.cairo'],
     calendar: ['calendar', '/.calendar/file', '/share/calendar/any/calendar.file', '/share/calendar/calendar.file', 'any/share/calendar/any/calendar.file', 'any/share/calendar/calendar.file'],
+    cangjie: ['file.cj'],
     capnp: ['file.capnp'],
     catalog: ['catalog', 'sgml.catalogfile', 'sgml.catalog', 'sgml.catalog-file'],
     cdc: ['file.cdc'],

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1647,
 /**/
     1646,
 /**/