Feedback about mount-and-assigns

[UniekLee]

In the "The %Socket{} data structure" section, the text references the assigns/2 function - that should be the assign/2 function (singular). Same goes for 3rd bullet point in the recap.

Additionally, the "Rendering assigns" section talks about changing the name of the assigns argument and the error it produces - that was a little hard to understand, and could do with a code sample to demonstrate what is being changed to generate that error.