Incorrect default for glob copy `options.overwrite`

[pettinen]

When copying, options.overwrite should default to true, as documented https://github.com/gregnb/filemanager-webpack-plugin/blob/07b977950bddd6aa50be097c1ad460fce550dbfa/src/options-schema.ts#L38-L42

However when the copy source is a glob and overwrite is not specified, fsExtra.copy is called with { overwrite: undefined }, which fs-extra interprets as { overwrite: false }: https://github.com/gregnb/filemanager-webpack-plugin/blob/07b977950bddd6aa50be097c1ad460fce550dbfa/src/utils/glob-copy.ts#L55-L58

This is also an undocumented breaking change between v8.0.0 and v9.0.0.