Use Dependabot to update Go modules

[cbandy]

The golang.org/x modules are a frequent source of vulnerabilities. Let's update them regularly to keep security fixes small.

Checklist:

• [x] Have you added an explanation of what your changes do and why you'd like them to be included?
• [x] Have you updated or added documentation for the change, as applicable?
• [x] Have you tested your changes on all related environments with successful results, as applicable?
  • [x] Have you added automated tests?

Type of Changes:

• [x] Testing enhancement

What is the new behavior (if this is a feature change)?

We'll get the following pull requests immediately, and then similar ones weekly. Any that we don't merge are updated and rebased weekly.

• https://github.com/cbandy/postgres-operator/pull/21
• https://github.com/cbandy/postgres-operator/pull/22
• https://github.com/cbandy/postgres-operator/pull/23

Other Information:

Dependabot validated the config file in my fork: https://github.com/cbandy/postgres-operator/runs/43355908899

[cbandy]

Dependabot validated the config file in my fork: https://github.com/cbandy/postgres-operator/runs/43355908899