Enable cert_expiry config entries

[cereal2nd]

Description:

This enables config entries for the cert_expiry component

Pull request with documentation for home-assistant.io (if applicable): home-assistant/home-assistant.io#10241

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• Untested files have been added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[cereal2nd]

are we still missing something in this PR?
it has been here for 25 days now and nothing happend with it

[MartinHjelmare]

There's a long queue of open PRs and only a few reviewers. Bigger PRs are also harder to find time for. Config entry PRs are inherently quite big.

[MartinHjelmare]

Looks great!

[MartinHjelmare]

Can be merged when build passes.