Link to vim syntax highlighting is outdated

[stefanhaerter]

Hello everybody,

it seems that the link here is outaded:

nunjucks/docs/templating.md

Line 42 in ea0d6d5

* vim <https://github.com/niftylettuce/vim-jinja>

I would want to provide a pull request, but I wanted to ask in advance to which repo the link could best be changed. After a quick search, I would suggest:

• https://github.com/lepture/vim-jinja
• https://github.com/Glench/Vim-Jinja2-Syntax