Show extended descriptions in lint popups

[Merrit]

Is your feature request related to a problem? Please describe.
Currently the hover information for lints only shows the short description of lint rules, which often fails to inform the user as to why or what to do instead, meaning you'd have to follow the link to the website if you didn't know already.

Describe the solution you'd like
I think the hover info should include the details of the rule which usually has an extended description and examples.

Additional context

An example of the current implementation, showing the camel_case_types rule:

This only includes the _desc property of the rule.

If it included the _details property it would include helpful context, and our lint popup could be more like:

Name types using UpperCamelCase. dart(camel_case_types) From the style guide: DO name types using UpperCamelCase. Classes and typedefs should capitalize the first letter of each word (including the first word), and use no separators. GOOD: class SliderMenu { // ... } class HttpRequest { // ... } typedef num Adder(num x, num y);

[DanTup]

Unfortunately it's not currently possible to use Markdown in Diagnostics in VS Code:

There's an open issue at microsoft/vscode#54272 requesting this - please add a 👍 to it, and if that's implemented (and then added to LSP), we may be able to add this.

Thanks!