Update documentation with DSL gradle implementation

[webuijorgeGL]

The documentation lacks the implementation for Gradle plugins with the declarative plugins block as Flutter 16 requested.

[ashish12s3]

@webuijorgeGL please provide more details

[assanbayev]

@webuijorgeGL
Have you figured out how to adapt it for the declarative plugins block, cause I'm facing some troubles. Could you help me please?
`Plugin [id: 'com.appdynamics.appdynamics-gradle-plugin', version: '22.2.2', apply: false] was not found in any of the following sources:

• Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
• Included Builds (No included builds contain this plugin)
• Plugin Repositories (could not resolve plugin artifact 'com.appdynamics.appdynamics-gradle-plugin:com.appdynamics.appdynamics-gradle-plugin.gradle.plugin:22.2.2')
  Searched in the following repositories:
  Google
  MavenRepo
  Gradle Central Plugin Repository`