ctrl+<number> not captured

When pressing ctrl+ only the number is received in the `Update` method.

**To Reproduce**

```go
func (t *Model) Update(msg tea.Msg) {
switch msg := msg.(type) {
case tea.KeyMsg:
if s := msg.String(); s == "ctrl+1" {
```
When pressing Ctrl+1 and evaluating `msg.String()` it returns "1"

**Expected behavior**
When pressing Ctrl+1 and evaluating `msg.String()` it returns "ctrl+1"