Quick-links for submitting feedback on features

[cjcenizal]

It would be great to be able to tailor the "Open an issue on GitHub" link in the header, or to be able to generate a "Provide feedback" button to embed in our apps that lets you prepopulate the issue with content. For example, a KibanaHelpButton component that can be used to like this:

<KibanaHelpButton feature="Painless lab" body="I have a suggestion for Painless Lab!" />

This component would render a feedback/suggestion icon button which has a url of https://github.com/elastic/kibana/issues/new?title=[Painless%20Lab]%20Your+suggestion+&body=I+have+a+suggestion+for+Painless+Lab and opens the link in a new tab. We could also define the GitHub issue template to use. See the GitHub automation docs for other options.

Developers can add custom links to the "Help" dropdown, but this content is difficult to discover and it also prevents you from creating multiple links in contexts where they make more sense (e.g. a flyout).

If we go the route of a component, I would suggest these props:

Prop	Behavior
feature	Prefixes the feature name to the title inside of brackets
body	Body content, perhaps unnecessary if we just hardcode an issue template instead
labels	Labels that get applied to the issue
children	The text of the button, which is rendered next to a "Feedback" icon. This prop may not even be necessary if we want to hardcore the text as "Give feedback on {feature}".
iconOnly	When set, this button is only rendered as a "Feedback" icon, with the children text rendered as a tooltip

[elasticmachine]

Pinging @elastic/kibana-core-ui (Team:Core UI)