Revert "neotest removed"

This reverts commit 94101216dc.

lua/custom/plugins/neotest-dotnet.lua

@@ -0,0 +1,14 @@
+return {
+  'nvim-neotest/neotest',
+  dependencies = {
+    'Issafalcon/neotest-dotnet',
+  },
+  config = function()
+    require('neotest').setup {
+      adapters = {
+        require 'neotest-dotnet',
+      },
+      discovery_root = 'solution',
+    }
+  end,
+}