Format blueprint descriptions with markdown

[thomasloven]

Proposed change

Blueprints can get pretty complex. Being able do describe them well would help.

Can this be abused? Yes.
Does that make it a bad idea? No.

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

blueprint:
  name: Time of Day - Manager
  description: |
    ## Keeps track of Time of Day.

    This requires you to set up an `input_select` [helper entity](/config/helpers) which has the following options:

    * morning
    * day
    * evening
    * night

    Whenever the time of day changes, the event `TOD_UPDATE` is fired. You can use this event as a trigger for your automations, and either look at the `tod` parameter of the event data or the current state of the `input_select` to determine the current Time of Day.

  domain: automation
  input:
...

Additional information

• This PR fixes or closes issue: fixes #
• 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]

Is the red of the link a theme, or does it miss styling?

[thomasloven]

That's just my theme for the dev instance.