Add prefer first or null rule

[byshy]

This PR has changes from this PR, please make sure to review that first

What's new?

• Adding a new rule that prefers the use of firstOrNull instead of first on iterables and its derivatives

[santitigaga]

@byshy Amazing, this is a useful rule.
Please add this new rule in the documentation in the gh-pages-source branch

[byshy]

I handled the comments above
I'm thinking about adding all the rules at once to the gh-pages-source, is that okay? or do you prefer to add them now?

[santitigaga]

I handled the comments above I'm thinking about adding all the rules at once to the gh-pages-source, is that okay? or do you prefer to add them now?

it's ok add all rules in one PR

[santitigaga]

Amazing !!!