patch 9.1.0826: filetype: sway files are not recognized

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

References:
 https://github.com/FuelLabs/sway.

Comments taken from their syntax documentation. File extension taken
from the same documentation/GitHub's own recognition of these file types

closes: #15973

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

src/testdir/test_filetype.vim

@@ -729,6 +729,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     svelte: ['file.svelte'],
     svg: ['file.svg'],
     svn: ['svn-commitfile.tmp', 'svn-commit-file.tmp', 'svn-commit.tmp'],
+    sway: ['file.sw'],
     swayconfig: ['/home/user/.sway/config', '/home/user/.config/sway/config', '/etc/sway/config', '/etc/xdg/sway/config'],
     swift: ['file.swift', 'file.swiftinterface'],
     swiftgyb: ['file.swift.gyb'],

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    826,
 /**/
     825,
 /**/