chore(vim): add mapping to exit completion

This is when inside a snippet the tab get taken over by the completion
menu, you can then not jump to the next mark in the snippet.

Now you can use <C-e> to close the completion menu and tab will then
jump to the next mark in the snippet.

site-modules/core/files/vim/plugin/completion.lua

@@ -10,6 +10,7 @@ cmp.setup({
     mapping = cmp.mapping.preset.insert({
         ['<C-j>'] = cmp.get_config().mapping['<Down>'],
         ['<C-k>'] = cmp.get_config().mapping['<Up>'],
+        ['<C-e>'] = cmp.mapping.abort(),
         ['<CR>'] = cmp.mapping(function(_fallback)
             if cmp.visible() then
                 cmp.confirm({ select = true })