Superglobals and documentation

[Orrison]

Add Superglobals rule and set up documenation.

[Copilot]

Pull Request Overview

This PR introduces a new SuperglobalsRule to detect unwanted usage of PHP superglobals, along with corresponding tests and documentation updates.

• Implements SuperglobalsRule to flag any direct use of PHP superglobals.
• Adds test fixtures and a default-options test covering all superglobals.
• Provides documentation (docs/Superglobals.md) and updates the main README.md to include the new rule.

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/Rules/Superglobals/config/configured_rule.neon	Registers the SuperglobalsRule for test scenarios
tests/Rules/Superglobals/Fixture/ExampleClass.php	Fixture demonstrating triggering and non-triggering cases
tests/Rules/Superglobals/DefaultOptionsTest.php	Verifies default behavior of the new rule
src/Rules/Superglobals/SuperglobalsRule.php	Implements the logic to detect superglobals usage
docs/Superglobals.md	Adds documentation for the Superglobals rule
README.md	Updates rules list to include Superglobals
.github/copilot-instructions.md	Adds Copilot instruction content (internal guidance)

Comments suppressed due to low confidence (1)

.github/copilot-instructions.md:124

• The changes in this file introduce internal Copilot instructions that should not be committed to the repository. Please remove or revert these additions to avoid repository pollution.

## Documentation Standards