feat: add diagnostic.displayByVimDiagnostic

set coc.nvim's diagnostics to nvim's `vim.diagnostic`, disabled by default.

This should be useful for nvim's diagnostic-related plugins that request diagnostic from `vim.diagnostic`

data/schema.json

@@ -938,6 +938,12 @@
       "description": "Use Ale, coc-diagnostics-shim.nvim, or other provider to display diagnostics in vim. This setting will disable diagnostic display using coc's handler. A restart required on change.",
       "default": false
     },
+    "diagnostic.displayByVimDiagnostic": {
+      "type": "boolean",
+      "scope": "language-overridable",
+      "description": "Display diagnostics with nvim's `vim.diagnostic`. This setting will disable diagnostic display using coc's handler. A restart required on change. Neovim only.",
+      "default": false
+    },
     "diagnostic.enable": {
       "type": "boolean",
       "scope": "language-overridable",

doc/coc.txt

@@ -1998,6 +1998,10 @@ b:coc_diagnostic_info					*b:coc_diagnostic_info*
 
 	can be used to customize statusline. See |coc-status|.
 
+b:coc_diagnostic_map					*b:coc_diagnostic_map*
+
+	Diagnostics of current buffer, the format is same as *diagnostic-structure*
+
 b:coc_current_function					*b:coc_current_function*
 
 	Function string that current cursor in.