Fix example from Documentation in Section 5

[jvfei]

Current Situation

copy and pasted first name, so where it should say last name and email is incorrect. https://idom-docs.herokuapp.com/docs/guides/adding-interactivity/index.html#section-5-dangers-of-mutability

Proposed Actions

correct the example

[Archmonger]

@jvfei Would you like to contribute a PR to resolve this? Would need to change this file.