Dependabot: `gradle` Kotlin and `composer` v2 support

Dependabot version updates now support

• Kotlin manifest files like .gradle.kts (gradle)
• PHP using the latest composer v2 (composer)

These are possible thanks to community contributions to Dependabot. If you’d like to contribute an improvement to Dependabot’s support for an existing ecosystem, check out Dependabot’s contributing guidelines. At this time, we’re taking a short break from accepting new ecosystem additions in order to update support for existing ecosystems.

To enable version updates and add support for these package managers, check in a dependabot.yml file with the specified package-ecosystem.