added transducer info to find-first and replace-nth docs

[ertugrulcetin]

It's more clear when docs says those fns can be used as transducers.

[weavejester]

Thanks. Please make sure your changes and the commit message adhere to the contributing guidelines.

[ertugrulcetin]

@weavejester changed the commit message 🙂

[weavejester]

Thanks, but the commit message is still past tense, not imperative mood, and over 50 characters. Instead, something like this:

Update find-first and replace-nth docstrings

With regard to the code, please ensure the docstrings wrap at 80 characters.

[ertugrulcetin]

@weavejester updated message with that one :) I'll try to follow this pattern, thanks.

[weavejester]

I notice you have three identically named commits. Can you squash them down?