Pin versions if using Renovate: Update config to best practices

[Copilot]

Updates the Renovate configuration to align with security best practices for dependency management and GitHub Action digest pinning.

Changes Made

• Replaced config:recommended with config:best-practices in the extends array
• Added helpers:pinGitHubActionDigestsToSemver to the extends array for GitHub Action digest pinning

Before

"extends": ["config:recommended"],

After

"extends": ["config:best-practices", "helpers:pinGitHubActionDigestsToSemver"],

This change improves the project's security posture by:

• Using Renovate's best practices configuration instead of the basic recommended config
• Enabling automatic pinning of GitHub Action digests to semver for better supply chain security

Related to the OpenTelemetry JS security scorecard findings at https://scorecard.dev/viewer/?uri=github.com/open-telemetry/opentelemetry-js

Fixes #46.

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