Add github copilot. Fix issue with lua and vim global

 * and add a couple more smaller vim plugins

lua/core/plugin_config/copilot.lua

@@ -0,0 +1,3 @@
+--highlight gray
+--highlight gray guifg=#5c6370
+vim.cmd[[highlight CopilotSuggestion ctermfg=8 guifg=white guibg=#5c6370]]

lua/core/plugin_config/init.lua

@@ -6,3 +6,4 @@ require("core.plugin_config.telescope")
 require("core.plugin_config.vim-test")
 require("core.plugin_config.lsp_config")
 require("core.plugin_config.gitsigns")
+require("core.plugin_config.copilot")

lua/core/plugin_config/lsp_config.lua

@@ -14,7 +14,20 @@ local on_attach = function(_, _)
 end
 
 require("lspconfig").sumneko_lua.setup {
-  on_attach = on_attach
+  on_attach = on_attach,
+  settings = {
+    Lua = {
+      diagnostics = {
+        globals = { "vim" },
+      },
+      workspace = {
+        library = {
+          [vim.fn.expand "$VIMRUNTIME/lua"] = true,
+          [vim.fn.stdpath "config" .. "/lua"] = true,
+        },
+      },
+    },
+  }
 }
 
 require("lspconfig").solargraph.setup {

lua/core/plugin_config/vim-test.lua

@@ -1,2 +1,6 @@
+vim.cmd [[
+  let test#strategy = "vimux"
+]]
+
 vim.keymap.set('n', '<leader>t', ':TestNearest<CR>')
 vim.keymap.set('n', '<leader>T', ':TestFile<CR>')

lua/core/plugins.lua

@@ -21,6 +21,9 @@ return require('packer').startup(function(use)
   use 'bluz71/vim-nightfly-colors'
   use 'vim-test/vim-test'
   use 'lewis6991/gitsigns.nvim'
+  use 'preservim/vimux'
+  use 'christoomey/vim-tmux-navigator'
+  use 'github/copilot.vim'
 
   use {
     "williamboman/mason.nvim",