Corp with other markdown syntax plugins

[tyru]

Current Status

Currently, this plugin only works with tpope/vim-markdown. This is included in runtime files but currently included one does not corp with markdown-codehl-onthefly.vim (tpope/vim-markdown#92).

Other markdown syntax plugins

• [x] tpope/vim-markdown
  • https://github.com/tpope/vim-markdown/pull/92
  • Seems not included in Vim runtime files
• [ ] gabrielelana/vim-markdown
• [ ] rcmdnk/vim-markdown
• [ ] plasticboy/vim-markdown

[tyru]

Updated issue text according to README.md.