chore: rename StartReturningModel to Run

Added aliases for the old functions, but deprecated them.

tutorials/basics/README.md

@@ -200,7 +200,7 @@ The last step is to simply run our program. We pass our initial model to
 ```go
 func main() {
     p := tea.NewProgram(initialModel())
-    if err := p.Start(); err != nil {
+    if _, err := p.Run(); err != nil {
         fmt.Printf("Alas, there's been an error: %v", err)
         os.Exit(1)
     }

tutorials/basics/main.go

@@ -79,7 +79,7 @@ func (m model) View() string {
 
 func main() {
 	p := tea.NewProgram(initialModel())
-	if err := p.Start(); err != nil {
+	if _, err := p.Run(); err != nil {
 		fmt.Printf("Alas, there's been an error: %v", err)
 		os.Exit(1)
 	}

tutorials/commands/README.md

@@ -169,7 +169,7 @@ as a `struct` with defaults.
 
 ```go
 func main() {
-    if err := tea.NewProgram(model{}).Start(); err != nil {
+    if _, err := tea.NewProgram(model{}).Run(); err != nil {
         fmt.Printf("Uh oh, there was an error: %v\n", err)
         os.Exit(1)
     }

tutorials/commands/main.go

@@ -71,7 +71,7 @@ func (m model) View() string {
 }
 
 func main() {
-	if err := tea.NewProgram(model{}).Start(); err != nil {
+	if _, err := tea.NewProgram(model{}).Run(); err != nil {
 		fmt.Printf("Uh oh, there was an error: %v\n", err)
 		os.Exit(1)
 	}