update readme with more information

[devoncarew]

Now that this package is published, we should update the readme with a bit more information:

• what's the package? what's it used for?
• a (brief) code example?
• references to more comprehensive documentation

cc @polina-c

[polina-c]

The package is still under construction and is constantly changing.
It is published for internal use only for now.
As soon as the package stabilizes, I will update readme.

This task is tracked under flutter/devtools#3951

So, closing this issue as duplicate

[devoncarew]

It is published for internal use only for now.

Gotcha, understood. FYI, I updated the status at https://pub.dev/packages/leak_tracker/admin to 'unlisted'; that means the package will not show on pub.dev search results. You can toggle that back at any time once this package is meant to be more visible.

[devoncarew]

We should update the readme with the info in the first comment (for both packages leak_tracker and leak_tracker_testing). They're both published, in tools.dart.dev, and on non pre-release versions; we really need more than 'coming soon'.