docs: remove the step to add mapper implementation

[tpluscode]

also added imports make it clear what is needed for the code

As a side note, I think it's rather redundant to include the instructions separate for JS and TS. They are virtually identical

[AlexZeitler]

Thanks for the feedback regarding JS/TS docs. I was thinking a lot about if this is necessary and just pushed both waiting for feedback like this.

If you like, you can remove one of them. I tend to remove the TS version as JS is the lowest common denominator.

[AlexZeitler]

@tpluscode Do you want to remove the duplicate JS/TS parts or do you want me to merge the current state of the PR?

[tpluscode]

In a separate PR maybe

[AlexZeitler]

Thanks 📦 version 0.1.1 has been published on npm.