[BUG] Don't mutate passed configuration options

[maschwenk]

The markdown initializer mutates the options you pass it. I don't see any obvious reason why this is necessary?

Redcarpet::Markdown.new(Redcarpet::Render::HTML.new({ bizzle: 'zizzle' }.freeze), {})

RuntimeError: can't modify frozen Hash
from (pry):5:in `merge!'

Instead just merge and return a new hash 👍 👎 🤷‍♂️

[maschwenk]

@robin850 Just a friendly bump on this?

[maschwenk]

@robin850 another friendly 🙏 bump?

[robin850]

Sorry for the late answer ; thank you very much for the patch @maschwenk ! 🎉 I took the liberty to write a more explicit test for that in the aforementioned commit and give you credit in the changelog.

[maschwenk]

Haha great! I literally almost closed this yesterday because I was losing faith, glad I didn't :)