Added "Shade" plugin (valentino-sm fork, original is unmaintained)

lua/plugins/shade.lua

@@ -0,0 +1,9 @@
+return {
+    "valentino-sm//shade.nvim",
+    config = function ()
+        require("shade").setup({
+            overlay_opacity = 50,
+            opacity_step = 1,
+        })
+    end
+}