lang/beancount: add beancount-langserver support
lang/beancount: add beancount-langserver support

Mentioned in #5035.
Remove when emacs-lsp/lsp-mode#2863 is resolved.

hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs