feat(runtime): new checkhealth filetype (#16708)

runtime/syntax/checkhealth.vim

@@ -0,0 +1,28 @@
+" Vim syntax file
+" Language:     Neovim checkhealth buffer
+" Last Change:  2021 Dec 15
+
+if exists("b:current_syntax")
+  finish
+endif
+
+runtime! syntax/markdown.vim
+unlet! b:current_syntax
+
+syn case match
+
+" We do not care about markdown syntax errors
+syn clear markdownError
+
+syn keyword healthError ERROR[:] containedin=markdownCodeBlock,mkdListItemLine
+syn keyword healthWarning WARNING[:] containedin=markdownCodeBlock,mkdListItemLine
+syn keyword healthSuccess OK[:] containedin=markdownCodeBlock,mkdListItemLine
+syn match healthHelp "|.\{-}|" containedin=markdownCodeBlock,mkdListItemLine contains=healthBar
+syn match healthBar  "|" contained conceal
+
+hi def link healthError Error
+hi def link healthWarning WarningMsg
+hi def healthSuccess guibg=#5fff00 guifg=#080808 ctermbg=82 ctermfg=232
+hi def link healthHelp Identifier
+
+let b:current_syntax = "checkhealth"