Fix KeepAlive Interval and Expose Error Callback

[dvonthenen]

Proposed changes

This PR contains the following changes:

• The WS protocol should ping every 20 seconds
• The Deepgram protocol should ping with KeepAlive every 5 seconds
• Exposes the Error Callback in the Live interface as it might be useful for recovery scenarios
• Consistency for singular versus plural where it makes sense in the struct names
• KeepAlive messages are disabled by default but can be optionally enabled.

Types of changes

What types of changes does your code introduce to the community Go SDK?
Put an x in the boxes that apply

• Bugfix (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 not work as expected)
• Documentation update or tests (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

All examples work!!