docs: using markdown in component slots (docs #2401)

[petedavisdev]

Summary

Documentation on how to use markdown in component slots with:

• code examples for single slot and named slots with empty lines before and after markdown,
• warning about not using # shorthand for named slots.

This is an awesome feature that deserves to be documented so that people know it's available and understand how to use it correctly.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[petedavisdev]

Preview of added content here

[Matthew-Benson]

Any update on this? I wanted to render markdown in a component and read through docs and issues for an hour before stumbling on this PR. Would have been very helpful to find this information quickly.