Add buffer deletion command and update source keymap, configure lsp_lines, null-ls, and trouble plugins

lua/custom/plugins/null-ls.lua

@@ -0,0 +1,12 @@
+return {
+  "jose-elias-alvarez/null-ls.nvim",
+  config = function()
+    local null_ls = require("null-ls")
+    null_ls.setup({
+      source = {
+        null_ls.builtins.diagnostics.eslint,
+        null_ls.builtins.completion.spell,
+      }
+    })
+  end
+}