[Docs] Clarify that es6 env also sets ecmaVersion to 6

[astorije]

What issue does this pull request address?

None, this is a documentation-only pull request.

What changes did you make? (Give an overview)

Reading the docs, it is not clear why ESLint's parser will stop complaining about ES6 specifics when es6 env is set and ecmaVersion: 6 is omitted.
It is actually done on purpose, but the documentation didn't mention this at all.

Is there anything you'd like reviewers to focus on?

N/A

[eslintbot]

Thanks for the pull request, @astorije! I took a look to make sure it's ready for merging and found some changes are needed:

• The commit summary needs to begin with a tag (such as Fix: or Update:). Please check out our guide for how to properly format your commit summary and update it on this pull request.
• Pull requests with code require an issue to be mentioned at the end of the commit summary, such as (fixes #1234). Please update the commit summary with an issue (file a new issue if one doesn't already exist).

Can you please update the pull request to address these?

(More information can be found in our pull request guide.)

[eslintbot]

LGTM

[ilyavolodin]

Thanks for PR!

[platinumazure]

Oh drat, I was going to ask if clarification might be needed for non-default parsers (which may not use ecmaVersion at all).

@ilyavolodin Do we need to talk about non-default parsers here? Maybe not, but wanted to ask.

[ilyavolodin]

I don't think we need to. We don't really focus on other parsers anywhere in our documentation. While we say we support them, I feel like if you choose any parser other than default, that sort of voids your warranty in regards to documentation:-)