[skip ci] fix(vim): unhighlight unescaped underscores in Markdown doc…

…uments

files/.vim/after/syntax/markdown.vim

@@ -0,0 +1,23 @@
+" Stop highlighting unescaped underscores in the middle of a word as an error.
+"
+" Consistency is key, and with the way things are now, people are more likely
+" to remove escaping instead of introducing it.
+"
+" While the original Markdown spec treats underscores in the middle of a word
+" as an emphasis [1], only 2 out of 28 implementations treat it that way
+" instead of treating it as a literal underscore at the time of writing [2].
+" Of the 2, Pandoc only does so in an opt-in strict mode. Prettier, a popular
+" formatter for Markdown, even unescapes them [3].
+"
+" While there are currently no settings to unhighlight individual errors [4]
+" [5], this fix takes care not to unhighlight any other errors that might get
+" added in the future [6].
+"
+" [1]: https://daringfireball.net/projects/markdown/syntax#em
+" [2]: https://babelmark.github.io/?text=foo_bar_baz
+" [3]: https://github.com/prettier/prettier/issues/3728
+" [4]: https://github.com/tpope/vim-markdown/issues/21
+" [5]: $VIMRUNTIME/syntax/markdown.vim (jump to file with gf)
+" [6]: See :help :syn-transparent
+syn match markdownIgnore "\w\@<=_\w\@=" transparent contains=NONE
+syn cluster markdownInline add=markdownIgnore