Add markdown syntax support for indented code blocks.

syntax/vimwiki_markdown.vim

@@ -79,9 +79,10 @@ let s:markdown_syntax.number_types = ['1.']
 let s:markdown_syntax.list_markers = ['-', '*', '+', '1.']
 let s:markdown_syntax.rxListDefine = '::\%(\s\|$\)'
 
-" Preformatted text
+" Preformatted text (code blocks)
 let s:markdown_syntax.rxPreStart = '\%(`\{3,}\|\~\{3,}\)'
 let s:markdown_syntax.rxPreEnd = '\%(`\{3,}\|\~\{3,}\)'
+let s:markdown_syntax.rxIndentedCodeBlock = '^\s*\n\(\(\s\{4,}[^ ]\|\t\+[^\t]\).*\n\)\+\(^\s*\n\)'
 
 " Math block
 let s:markdown_syntax.rxMathStart = '\$\$'

syntax/vimwiki_markdown_custom.vim

@@ -190,7 +190,9 @@ syntax match VimwikiTableRow /^\s*|.\+|\s*$/
                            \ VimwikiEqInT,
                            \ @Spell
 
-
+" indented code blocks https://github.github.com/gfm/#indented-code-blocks
+execute 'syntax match VimwikiIndentedCodeBlock /' . vimwiki#vars#get_syntaxlocal('rxIndentedCodeBlock') . '/'
+hi def link VimwikiIndentedCodeBlock VimwikiPre
 
 " syntax group highlighting
 hi def link VimwikiImage VimwikiLink