patch 9.1.1549: filetype: pkl files are not recognized

Problem:  filetype: pkl files are not recognized
Solution: detect *.pkl files as pkl filetype, include
          a filetype plugin (Riley Bruins)

References:
https://pkl-lang.org/
https://github.com/apple/pkl

closes: #17751

Signed-off-by: Riley Bruins <ribru17@hotmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -605,6 +605,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     pilrc: ['file.rcp'],
     pine: ['.pinerc', 'pinerc', '.pinercex', 'pinercex'],
     pinfo: ['/etc/pinforc', '/.pinforc', 'any/.pinforc', 'any/etc/pinforc'],
+    pkl: ['file.pkl'],
     pli: ['file.pli', 'file.pl1'],
     plm: ['file.plm', 'file.p36', 'file.pac'],
     plp: ['file.plp'],

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1549,
 /**/
     1548,
 /**/