Add a keymap to easily add {{site.url))/ before

...some text

This is useful when writing my daily emails and creating links within
the content.

modules/home-manager/cli/neovim/config/after/ftplugin/markdown.lua

@@ -1,3 +1,5 @@
 -- TODO: Interim fix for https://github.com/nvim-treesitter/nvim-treesitter-context/issues/431.
 vim.opt_local.spell = true
 vim.opt_local.wrap = true
+
+vim.keymap.set("n", "<leader>su", "Bi{{site.url}}/<Esc>")