Add three more sentences about what Octane is to the Octane page

[jenweber]

We should add 2-3 quick "marketing" focused sentences directly to the Octane page, at the very beginning.

To-do:

• draft additions/edits for the octane page, using some of the feedback and suggestions below. These are rough suggestions so it's up to you to figure out wording.
• check to see if messaging is consistent with editions/index and the upgrading section of the Octane guides preview
• If there are inconsistencies, include changes to editions in the same PR, and open an issue in the Guides for the Upgrading page. Link to it here.

Feedback from @chriskrycho:

I'm thinking something very roughly like:

• Modern JavaScript, with ES6 classes, decorators, async/await, and zero-config npm interop
• A lighter-weight component API, including syntax for better readability
• No need for jQuery, legacy classes (.extend() and .create() etc.), or computed properties

I shared https://emberjs.com/editions/octane/ with some folks, and a dev who really likes Ember but has been doing other stuff for the last couple years looked at it and wrote: "That page doesn't seem to explain what Ember Octane is"

It seems like we probably need something like a super condensed version of https://octane-guides-preview.emberjs.com/release/upgrading/editions/ and the Roadmap on that page, just for pure marketing reasons, presumably with links to more details.
Is there any place we have a short summary of "Here's what's new!"? Like https://octane-guides-preview.emberjs.com/release/upgrading/editions/#toc_features-overview, I guess?

[chriskrycho]

Thanks to @jamonholmgren for the immediate feedback when I sent him the link to https://emberjs.com/editions/octane/!

[MelSumner]

I think we should ask the marketing team for help with this! 👍

[stale]

This issue has been automatically marked stale. If this issue is something that still needs work, please add a comment and it will remain open, otherwise it will close in 7 days. You are welcome to open a new issue if you miss the window. Thanks!

[MelSumner]

leave it open please stale bot.

[stale]

This issue has been automatically marked stale. If this issue is something that still needs work, please add a comment and it will remain open, otherwise it will close in 7 days. You are welcome to open a new issue if you miss the window. Thanks!

[amyrlam]

added pinned label, keeps things not stale per https://github.com/ember-learn/ember-website/blob/master/.github/stale.yml#L14