TF-495 Add document for linter plugin

docs/adr/0004-linter.md

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+# 3. Integrate linter into app
+
+Date: 2022-04-22
+
+## Status
+
+Accepted
+
+## Context
+
+- Use linter to encourage good coding practices
+- Helps optimize and increase application performance
+
+## Decision
+
+- To use we follow these steps:
+    + Depend on this package as a `dev_dependency` by running `flutter pub add --dev flutter_lints`.
+    + Create an `analysis_options.yaml` file at the root of the package (alongside the `pubspec.yaml` file) and include: `package:flutter_lints/flutter.yaml` from it.
+
+## Official document
+
+- [flutter_lints](https://pub.dev/packages/flutter_lints)
+
+## Consequences
+
+- The code is written standard according to the linter toolkit. Performance is improved.