nvim-lspconfig already has shortcuts to declaration/definition with "gd"
and "gD", but in testing, they did not behave the same as the shortcuts
defined in this commit for some reason.
<leader>d and <leader>D are the shortcuts defined for
definition/declaration (<leader> is by defalt back-slash "\").
Show floating diagnostic changed to <leader>F.
Comments in init.lua.
(<leader> is backspace usually.)
Disable "q" mappings, set "<leader>q" to use quick-comment.
Set "<leader>f" to use treesitter-fold.
Set "<leader>l" to load lsp-plugins.
