Add prefer-math-trunc rule

[noftaly]

Added prefer-math-trunc rule, which forbids the use of | 0 over Math.trunc() to truncate numbers.
One thing i'm not really sure about is the error message. It says not to use | 0 to truncate numbers, but maybe it should say no to use bitwise OR with 0? Idk, let me know what you think of.

Fixes #827

[noftaly]

I have a question: What to do with variables (or member expressions)? The fix can break one's code because undefined | 0 gives 0, but Math.trunc(undefined) gives NaN...
What should we do?
One way of doing it would be to add a || 0 for the autofix, when it is a variable/object. Like that, foo = bar | 0 would become foo = Math.trunc(bar || 0). But this does not resolve the case where the variable contains a string for example (because 'a' | 0 gives 0)

[sindresorhus]

The rule name could be improved though:

• no-bitwise-number-truncation
• prefer-math-trunc

[papb]

I like prefer-math-trunc 👍

[noftaly]

I renamed the rule and adressed all reviews :)
The CI seems to be failing, but because of another rule, not prefer-math-trunc. npm run test is successful on my laptop, which is up to date with this PR...
nevermind, i just did not sort the rule alphabetically after renaming it.

[fisker]

Please add some cases that have comments inside or around. Also some parenthesized cases.

[sindresorhus]

Nice work, @noftaly 👍🏻