Updated readme

[chirag-patel-rp]

@HancilSequeira let's also add what the function returns, store it in some variable and lay down the attributes of that variable

Example: $card = $api->card->fetch($cardId);

Now also add how this $card return variable looks like, you can have this object defined somewhere and then reference to not repeatedly define $card object

[HancilSequeira]

@chirag-patel-rp do I need to add response for all the API or is it ok if I had only one response for any API

[chirag-patel-rp]

@HancilSequeira yes for all API responses, you can create a common object and then link that in the document to avoid repetitiveness.

For example, create a document of entity.md and there list all entity objects (like: order, payment, transfer) and then start referring those in the API response