chore: Setup Dependabot, set Yarn version to v4

[cgero-eth]

Description

• Set Yarn version to v4 (see https://yarnpkg.com/getting-started/install)
• Setup Dependabot

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran all tests with success and extended them if necessary.
• I have updated the CHANGELOG.md file in the root folder of the package after the [UPCOMING] title and before
  the latest version.
• I have tested my code on the test network.

[thekidnamedkd]

LGTM. Corepack + Dependabot will be very handy. Is there anything we can do over on the app with the dependencies? 🙃

[cgero-eth]

LGTM. Corepack + Dependabot will be very handy. Is there anything we can do over on the app with the dependencies? 🙃

Sure we could introduce Dependabot on the App as well, but given that we're rebuilding it I'm not sure if it makes sense to invest time to update old dependencies there. Let's discuss this on the next tech talk anyway because it might be worth it 👌🏻