feat: Ability to create/specify Service Account

[SurelyMario]

Description

This PR adds the ability to automatically create a service account for selenium-grid deployment. By default, a service account by the name of selenium-serviceaccount will be made. This functionality can be disabled with .serviceAccount.create: false and a pre-existing service account can be specified via .serviceAccount.name.

Both .spec.serviceAccountName and .spec.serviceAccount were added to maintain some backwards compatibility.

Also minor nit-pick, I removed a duplicate key in .ingress.

Motivation and Context

I wanted it for my environment and also #1783 needed it so why not.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[SurelyMario]

I'm gonna be honest, I don't know if some sort of generator was used for README.md so I haven't updated it, @diemol some guidance would be appreciated here.

[diemol]

README.md was manually created.

[diemol]

I can merge when instructions on how to use this are added to the read me.

[diemol]

Thank you, @SurelyMario!