Add support for service objects

[rxbchen]

Description

Add support for k8s Services Object

Type of change

• Bug fix 🐛
• New feature ✨
• This change requires a documentation update 📖
• Breaking changes ⚠️

Checklist:

• I have 🎩 my changes (A 🎩 specifically includes pulling down changes, setting them up, and manually testing the changed features and potential side effects to make sure nothing is broken)
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The test coverage did not decrease
• I have signed the appropriate Contributor License Agreement

[genevieveluyt]

Can you also add it to https://github.com/Shopify/kubeaudit/blob/public-pkg/pkg/k8s/helpers.go#L50 and potentially https://github.com/Shopify/kubeaudit/blob/public-pkg/pkg/k8s/helpers.go#L120 if applicable

EDIT: And also https://github.com/Shopify/kubeaudit/tree/public-pkg/internal/test/fixtures/all_resources and https://github.com/Shopify/kubeaudit/blob/public-pkg/internal/k8sinternal/client.go#L91 😄

[ghost]

Congrats on merging your first pull request, keep em coming!