add lsp_signature

lua/custom/plugins/lsp_signature.lua

@@ -0,0 +1,15 @@
+return {
+  'ray-x/lsp_signature.nvim',
+  event = 'InsertEnter',
+  opts = {
+    bind = true,
+    doc_lines = 0,
+    close_timeout = 1000,
+    handler_opts = {
+      border = 'rounded',
+    },
+  },
+  config = function(_, opts)
+    require('lsp_signature').setup(opts)
+  end,
+}