[Forms] Use regular JavaScript functions in the examples

[jennevdmeer]

There is no real point to use const for functions. While it surely is an opinion, the arrow syntax should only be used for anonymous functions and it seems more confusing for newer people.

• To me and I would assume a new user function (...) { is instantly more clearer that we are working with a function instead of a variable
• Function has no name during debugging when using arrow syntax
• Its not shorter function foo(e) { vs const foo = (e) => {
• Hoisting is weird, specially for newer people (https://stackoverflow.com/a/33040926)

I also changed the introduction line to the delete button part to detail what the user is going to do in following code block which seemed a little unclear to me personally. If the writing is not ok, please change it.

[javiereguiluz]

Jenne, you explained it perfectly why this change is a good thing and I fully agree on that, so this is now merged.

While merging we did a very minor change (see 91c545f) because in the docs we never use "we", "our", etc. because the docs are written from the point of view of the reader, so we only use "you", "your", etc.