[TSVB] Make markdown across Kibana consistent

[alexwizp]

Summary

Fix: #14436. GFMD (GitHub Flavored Markdown Spec) checked

Release Summary: TSVB now uses the same markdown parser than the Markdown visualization.

Before:

After:

Checklist

• This was checked for cross-browser compatibility, including a check against IE11
• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• This was checked for keyboard-only and screenreader accessibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This includes a feature addition or change that requires a release note and was labeled appropriately

[markov00]

LGTM. Tested locally and now it display nicely!
Please can you change the title of this PR to include TSVB? We still have some components that use a different markdown implementation MarkdownSimple and I think it's better keep that title when we will finally have a single implementation across kibana :)

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request

[elasticmachine]

Pinging @elastic/kibana-app

[timroes]

Code LGTM