Fix LSP and update plugins

- Structure LSP configuration code
- Since `lsp-zero` is deprecated, instead use `nvim-lspconfig`
- Use `nvim_lsp_signature_help` instead of `lsp_signature`

nvim/lua/config/theme.lua

@@ -2,7 +2,7 @@ require('nightfox').setup({
     options = {
         transparent = true,      -- Disable setting background
         terminal_colors = true,  -- Set terminal colors (vim.g.terminal_color_*) used in `:terminal`
-        dim_inactive = false,    -- Non focused panes set to alternative background
+        dim_inactive = false,    -- Non-focused panes set to alternative background
         module_default = true,   -- Default enable value for modules 
     },
     palettes = {