Adding extension using gradle plugin erase gradle config files content

[ia3andy]

Describe the bug
When adding an extension using gradle plugin:

$ ./gradlew addExtension --extensions="io.quarkus:quarkus-resteasy-jackson"
Starting a Gradle Daemon (subsequent builds will be faster)

> Task :addExtension
✅ Adding dependency io.quarkus:quarkus-resteasy-jackson:jar

BUILD SUCCESSFUL in 49s
1 actionable task: 1 executed

It erases gradle config files content:

• build.gradle
• gradle.properties
• settings.gradle

Expected behavior
It should update the files with the new extension but not erase it.

To Reproduce
Steps to reproduce the behavior:

1. Create a gradle project
2. Add an extension using ./gradlew addExtension --extensions="..."
3. Check the files

Environment (please complete the following information):

• Quarkus version or git rev: 0.24.0