Fix strong tag

[mccraveiro]

Marked version: master branch

Markdown flavor: CommonMark

Description

• Related to Defibrillator challenge #1216

Input

foo _____

Expectation

<p>foo _____</p>

Result

<p>foo <strong>_</strong></p>

What was attempted

Not matching the strong tag when the same character is the content

Contributor

• Test(s) exist to ensure functionality and minimize regression (if no tests added, list tests covering this PR); or,
• no tests required for this PR.
• If submitting new feature, it has been documented in the appropriate places.

Committer

In most cases, this should be a different person than the contributor.

• Draft GitHub release notes have been updated.
• CI is green (no forced merge required).
• Merge PR