after/ftplugin/html.vim

Enforce vim script implementation to reduce ambiguities and improve robustness:

scriptversion 4

I treat MHTML files as HTML, so make it possible to use section jumps to jump about:

if expand('%:e') ==? 'mhtml'
    nnoremap <buffer> ]]
    \   <Cmd>call search('^------MultipartBoundary--', '')<CR>
    nnoremap <buffer> [[
    \   <Cmd>call search('^------MultipartBoundary--', 'b')<CR>
endif