Update javascript-styleguide packages to be compatible with eslint v9 (#170)

# Justification

Upgrades to eslint v9. Resolves #155

# Implementation

- Remove all the legacy config files and replace them with flat config
files.
- Update the configurations to use [flat config
format](https://eslint.org/docs/latest/use/configure/migration-guide)
- Update the dependencies version that support eslint v9.
- Update the READMe doc related to this eslint v9 change.

# Testing

- Packed and applied the updated style guide in our client app - linting
passed successfully.

Author: gokulprasanth-ni

.github/CODEOWNERS

@@ -1,4 +1,4 @@
-# Copyright (c) 2023 National Instruments
+# Copyright (c) 2025 National Instruments
 
 # Each line is a file pattern followed by one or more owners.
 # More info: https://docs.github.com/en/github/creating-cloning-and-archiving-repositories/creating-a-repository-on-github/about-code-owners

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2021 National Instruments Corporation
+Copyright (c) 2025 National Instruments Corporation
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Update eslint-config-angular to be compatible with eslint v9. Change default rule configuration to assume `strictNullChecks` is enabled. See [Migration Guide](https://github.com/ni/javascript-styleguide/blob/main/README.md#migrating-to-eslint-flat-configuration-format) for more information.",
+  "packageName": "@ni/eslint-config-angular",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

change/@ni-eslint-config-angular-2b894e10-2f6e-4ff2-ade2-fae0335c38d8.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Update eslint-config-javascript to be compatible with eslint v9. See [Migration Guide](https://github.com/ni/javascript-styleguide/blob/main/README.md#migrating-to-eslint-flat-configuration-format) for more information.",
+  "packageName": "@ni/eslint-config-javascript",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

change/@ni-eslint-config-javascript-8342b44c-c3b9-4617-ac3e-8f4c3a14962c.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Update eslint-config-playwright to be compatible with eslint v9.  Change default rule configuration to assume `strictNullChecks` is enabled. See [Migration Guide](https://github.com/ni/javascript-styleguide/blob/main/README.md#migrating-to-eslint-flat-configuration-format) for more information.",
+  "packageName": "@ni/eslint-config-playwright",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

change/@ni-eslint-config-playwright-854caf08-4e79-4f67-b93a-441aa8e94aa6.json

@@ -0,0 +1,7 @@
+{
+  "type": "major",
+  "comment": "Update eslint-config-typescript to be compatible with eslint v9. Change default rule configuration to assume `strictNullChecks` is enabled. See [Migration Guide](https://github.com/ni/javascript-styleguide/blob/main/README.md#migrating-to-eslint-flat-configuration-format) for more information.",
+  "packageName": "@ni/eslint-config-typescript",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}