Add htmldjango (vim filetype) to languages

[nulty]

Description

Short version -

Vim and Neovim use filetypes to handle different files. For syntax, highlighting, and more.
Vim uses the filetype htmldjango for django templates.
The tailwindcss-language-server does not recognise htmldjango as a file language and so vim and neovim suffer as a result.

I would like to add htmldjango as a language upstream so individual configurations for lsp in the Vim world don't need to consider this issue.

Issue was raised in neovim/nvim-lspconfig repo. I think adding this line would be the most effective way to solve the issue.

I've built and tested this with neovim and it works.

[bradlc]

Looks good to me, thanks!