Feature/fix frozen strings

[prtngn]

Hi. I have a problem with frozen strings. This is PR fix it.

[janfri]

On which Ruby version does it not work?

[prtngn]

On which Ruby version does it not work?

Ruby is 3.1.1. This problem occurs when the global Frozen Litteral Strings flag is set at the project level.

[prtngn]

And this PR is not full ) I still need to improve it.

[janfri]

How about to add a line # frozen_string_literal: false at the top of mini_exiftool.rb? Then it should work when frozen_string_literal is globally set to true in your application.

I'm afraid that your optimizations could be counter productive, since you introduze arrays to avoid manipulation of Strings. It seems that setting frozen_string_literal to true is not so effective how it seems at the first think. See mame's reply: https://bugs.ruby-lang.org/issues/11473#note-59.

[prtngn]

Yes, # frozen_string_literal: false one of the solutions to the problem