The API for `window.set_items` took to many variable types. It would
take a table in multiple different formats and a string. Now it will
only take a table in a single format and a string. It will convert the
string into the table format by splitting it on new lines.
The table format is an array of tables that must have a `content` key
that will be the text that is displayed in the completion window. The
table can have any other data that is ignored.
```lua
local items = {
{ content = "Item one" },
{ content = "Item two" }
}
```
The `set_items` function will only display the `content` key in the
completion window, it will not do any sorting or filtering, that must be
done before passing the data to the `set_items` function.
