nvim: Improve lsp source chaining

Lsp will by default invoke most of its sources simultaneously (one after
the other if no completions are found for the first), but this is
disabled for pandoc.

In pandoc, only the buffer and lsp sources are invoked (the first
chain), since bibcite will take a while to compile the cite keys.
To invoke bibcite in pandoc, use c-j/c-k when in the completion menu,
and they will be calculated.

This may be removed if a faster compilation for bibtex citekeys is
found.

bootstrap/packages.txt

@@ -9,6 +9,7 @@ aspell-de
 aspell-en
 atool
 barrier
+bash-language-server
 bat
 bc
 biber
@@ -34,6 +35,7 @@ glances
 glow
 gnome-keyring
 go
+gopls
 grub
 hugo
 i3-gaps
@@ -90,6 +92,7 @@ psmisc
 pulsemixer
 python-black
 python-jedi
+python-language-server
 python-pdfminer.six
 python-pipx
 python-pybtex
@@ -115,6 +118,7 @@ surfraw
 sxhkd
 systemd-sysvcompat
 tdrop-git
+texlab
 texlive-bibtexextra
 texlive-fontsextra
 texlive-formatsextra
@@ -138,6 +142,7 @@ usbutils
 vagrant
 vi
 vifm
+vim-language-server
 xcape
 xclip
 xorg-xev