Refactor for better modularity (share more code among edit functions, rename "offline" package to "backend"

src/backend/initWIN.go

@@ -0,0 +1,25 @@
+//go:build windows
+
+package backend
+
+import (
+	"fmt"
+	"os"
+)
+
+const FallbackEditor = "nvim" // since there is no pre-installed CLI editor on Windows, default to the most popular one
+
+// dirInit creates the libmutton directories
+func dirInit() {
+	// create EntryRoot (includes config directory on Windows)
+	err := os.MkdirAll(EntryRoot, 0700)
+	if err != nil {
+		fmt.Println(AnsiError + "Failed to create \"" + EntryRoot + "\":" + err.Error() + AnsiReset)
+		os.Exit(1)
+	}
+}
+
+// textEditorFallback returns FallbackEditor
+func textEditorFallback() string {
+	return FallbackEditor
+}