Automatically upgrade dependencies with Renovate.

[bmarty]

Since Dependabot does not support gradle catalog (yet), our dependencies are not updated and we are starting to get some vulnerability reports.

Renovate is another app which can do this work: https://github.com/renovatebot/renovate

• install the app https://github.com/apps/renovate on the project.
• The app should create a PR. Once merge, the app will start creating PR to upgrade or dependency.

If this is working properly, we may consider deactivating Dependabot to having duplication.

[bmarty]

Configuration is finished, we may iterate in the future. The tool has created this PR: #147 and I have tweaked configuration in the file renovate.json.

For ref, the tool has created a dashboard issue: #150 that I have pinned to the project.

[bmarty]

What's remaining is:

• deactivate (or remove) Dependabot
• update the documentation about Dependabot

For now I want to check that Renovate are creating all the PR that Dependabot used to create (but I think this will be the case)