Add syntax & ftplugin for pymanifest (#12773)

runtime/syntax/pymanifest.vim

@@ -0,0 +1,44 @@
+" Vim syntax file
+" Language:	PyPA manifest
+" Maintainer:	ObserverOfTime <chronobserver@disroot.org>
+" Filenames:	MANIFEST.in
+" Last Change:	2023 Aug 12
+
+if exists('b:current_syntax')
+    finish
+endif
+
+let s:cpo_save = &cpoptions
+set cpoptions&vim
+
+syn iskeyword @,-
+
+" Comments
+syn keyword pymanifestTodo contained TODO FIXME XXX
+syn match pymanifestComment /\\\@1<!#.*/ contains=pymanifestTodo
+
+" Commands
+syn keyword pymanifestCommand
+            \ include exclude
+            \ recursive-include global-include
+            \ global-include global-exclude
+            \ graft prune
+
+" Globs & character ranges
+syn match pymanifestGlob /\*\|\*\*\|?/
+syn match pymanifestRange /\\\@1<!\[.\{-}\]/
+
+" Line break
+syn match pymanifestLinebreak /\\$\|\\\ze\s\+#/
+
+hi def link pymanifestCommand Keyword
+hi def link pymanifestComment Comment
+hi def link pymanifestGlob SpecialChar
+hi def link pymanifestLinebreak SpecialKey
+hi def link pymanifestRange Special
+hi def link pymanifestTodo Todo
+
+let b:current_syntax = 'pymanifest'
+
+let &cpoptions = s:cpo_save
+unlet s:cpo_save