Fix strict error handling in Markdown card templates

[frenck]

Proposed change

Adds strict error handling to the template rendering in the Markdown card.
Without it, things like undefined variables in template will end up in the Home Assistant logs (basically turning the Home Assistant log into a keylogger).

Ideally, this should be shipped in a patch release. I'm not sure how the frontend currently manages/classified PRs for that matter.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: home-assistant.log behaves like a keylogger core#70259
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

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

• Documentation added/updated for www.home-assistant.io

[bramkragten]

Should this just be done for markdown card, or by default?

[frenck]

Should this just be done for markdown card, or by default?

Good question... 🤷