nvim: moved viper highlighting to separate repository and imported it

.config/nvim/lua/plugins/viper-nvim.lua

@@ -0,0 +1,8 @@
+return {
+  -- highlighting for the viper verification language
+  "tiyn/viper.nvim",
+  event = { "BufReadPre *.vpr", "FileType viper" },
+  config = function()
+    require("viper").setup()
+  end,
+}