Update README.md (dart-archive/lints#18)

Author: mit-mit

pkgs/lints/README.md

@@ -1,5 +1,66 @@
 [![pub package](https://img.shields.io/pub/v/lints.svg)](https://pub.dev/packages/lints)
 [![Build Status](https://github.com/dart-lang/lints/workflows/validate/badge.svg)](https://github.com/dart-lang/lints/actions?query=branch%3Amain)
 
-This repo contains official Dart lint rules.
+# Official Dart lint rules.
 
+The Dart linter is a static analyzer for identifying possible problems in your
+Dart source code. More than a hundred [linter rules][rules] are available,
+checking anything from potential typing issues, coding style, and formatting.
+
+The current `package:lints` contains the official selections of lints that the
+Dart team encourages using.
+
+Two sets of lints are available:
+
+* ***Core lints***: Lints that help identify critical issues that are likely to
+lead to problems when running or consuming Dart code. All code should pass these
+lints.
+
+* ***Recommended lints***: Lints that help identify additional issues that may
+lead to problems when running or consuming Dart code, and lints that enforce
+writing Dart using a single, idiomatic style and format. All code is encouraged
+to pass these lints. The recommended lints include all the core lints.
+
+## Where these lints are used
+
+When creating new Dart project using the [`dart create`][dart create] command,
+the lints from `package:lints` are enabled by default.
+
+When uploading a package to the [pub.dev] package repository, packages are
+[awarded pub points][scoring] depending on whether they pass at least the 'core'
+lints (note: the recommended lints automatically include all core lints). 
+
+For documentation on the individual lints, see the [linter rules][rules] page on
+dart.dev.
+
+## How to enable these lints
+
+For new apps created with `dart create`, the lints are enabled by default.
+
+For existing apps or packages, take these steps to enable these lints:
+
+1. Add a *dev* dependency on this package to your `pubspec.yaml` file:
+
+```yaml
+dev_dependencies:
+  lints: ^1.0.0
+```
+
+2. Create a new `analysis_options.yaml` file, next to the pubspec, that includes
+the lints package:
+
+```yaml
+include: package:lints/core.yaml
+```
+
+## Customizing the pre-defined lint sets
+
+You can customize the pre-defined lint sets, both to disable one or more of the
+lints included, or to add additional lints. For details see [customizing static
+analysis].
+
+[dart create]: https://dart.dev/tools/dart-tool
+[scoring]: https://pub.dev/help/scoring
+[customizing static analysis]: https://dart.dev/guides/language/analysis-options
+[rules]: https://dart.dev/tools/linter-rules
+[pub.dev]: https://pub.dev