review and spell check documentation.

review and spell check documentation.

https://github.com/parrogo/writefs/blob/bafd5fe32d44355396aaac45e67b607e2f86c2cd/writefs.go#L21

```golang
)

// # TODO: review and spell check documentation.

// Flag is a type that represents the
// values accepted by OpenFile function
// flag argument.
```

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