Fix imports in model.go

I noticed that the non-stdlib imports were split into 2 groups, seemingly
randomly. No other files does this so I just brought it back to one group
and let goimports sort it.

Author: mmlb

internal/model/model.go

@@ -11,15 +11,14 @@ import (
 	"time"
 
 	"github.com/atotto/clipboard"
-	"github.com/maaslalani/slides/internal/file"
-	"github.com/maaslalani/slides/internal/navigation"
-	"github.com/maaslalani/slides/internal/process"
-
 	"github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/glamour"
 	"github.com/maaslalani/slides/internal/code"
+	"github.com/maaslalani/slides/internal/file"
 	"github.com/maaslalani/slides/internal/meta"
+	"github.com/maaslalani/slides/internal/navigation"
+	"github.com/maaslalani/slides/internal/process"
 	"github.com/maaslalani/slides/styles"
 )