[D8] Google Maps Services

Looks great, i didn't find any coding standard issue, I am able to call map services after module installation, moving this to rtbc.

I am changing priority as per https://www.drupal.org/node/539608.

Here is the result of the manual review:

1. Code looks good and follows Drupal best practices:
- route access is controlled by separate permission;
- configuration form looks good;
- configuration object has schema and default values;
- custom services use dependency injection;
2. I tried some examples from README file and it works as expected;
3. phpcs reported about some CS issues, so I reported about it in a new task: #3182737: Fix coding standards errors.

Overall, it looks good to me.

Some suggestions for maintainer:
1. Close #3170088: Automated Drupal 9 compatibility fixes, because the module is already Drupal 9 compatible;
2. Create a dev release, so we can see the diff between the last stable version and the ongoing development version;
3. Consider using some existing SDK (i.e. https://yidas.github.io/google-maps-services-php) or create your own to delegate some parts of the project.

Thanks!

The master branch isn't used for Drupal.org projects. The other branch needs to be made the default one, and the master one deleted.

Thank you for your contribution! I am going to update your account.

These are some recommended readings to help with excellent maintainership:

• Dries' post on Responsible maintainers
• Best practices for creating and maintaining projects
• Maintaining a drupal.org project with Git
• Commit messages - providing history and credit
• Release naming conventions.
• Helping maintainers in the issue queues

You can find more contributors chatting on the IRC #drupal-contribute channel. So, come hang out and stay involved.
Thank you, also, for your patience with the review process.
Anyone is welcome to participate in the review process. Please consider reviewing other projects that are pending review. I encourage you to learn more about that process and join the group of reviewers.

I thank all the dedicated reviewers as well.