update the readme to clarify the package's goals

[devoncarew]

• update the readme to clarify the package's goals (what's in scope and what's out of scope)
• fix Update the readme to clarify the goals and non-goals of this package #121
• prep for a publish

---

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[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:lints	2.1.1	ready to publish	v2.1.1

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[devoncarew]

thanks for the feedback - updated