[Docs] Introduce function parameters in the function page.

[RichardCoppin]

Where is the problem?

https://docs.modular.com/mojo/manual/functions

What can we do better?

My proposal is to introduce function parameters up front in the initial introduction of the function fn syntax.

Not doing so, places the reading with a mental "broken link". Anyone coming across the function parameter syntax in a code base or API reference for the first time will not be able to ascertain what this arcane syntax actually means.

Secondly, the footnote refers to the term parameters without any explanation of what that term means.

Once the function parameters have been introduced then place the hyperlink for the remainder of the discussion of parameters versus arguments.

TL;DR:

Function parameters need to be introduced here:

Anything else?

No response