[nvim] Update LSP and completion

.config/nvim/lua/plugins/lspconfig.lua

@@ -14,7 +14,12 @@ return {
     "williamboman/mason.nvim",
     lazy = false,
     config = function()
-      require("mason").setup()
+      require("mason").setup({
+        registries = {
+          "github:mason-org/mason-registry",
+          "github:Crashdummyy/mason-registry",
+        },
+      })
     end
   },
   {
@@ -23,5 +28,13 @@ return {
     opts = {
       auto_install = true,
     },
+  },
+  {
+    "seblyng/roslyn.nvim",
+    ---@module 'roslyn.config'
+    ---@type RoslynNvimConfig
+    opts = {
+      -- your configuration comes here; leave empty for default settings
+    },
   }
 }