feat: add configurations for memory only, disk only, and memory & disk modes

vfs/memory/memory.go

@@ -25,6 +25,10 @@ type MemoryFS struct {
 
 // New creates a new MemoryFS.
 func New(capacity int64) *MemoryFS {
+	if capacity <= 0 {
+		panic("memory capacity must be greater than 0") // panic if the capacity is less than or equal to 0
+	}
+
 	return &MemoryFS{
 		files:    make(map[string]*file),
 		capacity: capacity,