Surface @SerialName annotation in top-level documentation

[reddaly]

What is your use-case and why do you need this feature?

The @SerialName is a bit buried in the documentation

It took a few minutes for me to find that.

Describe the solution you'd like

Update the top-level README to contain an example of a custom field name, like so:

@Serializable
class Project(val name: String, @SerialName("lang") val language: String)