fix: failed commonmark examples 57 and 40

[Jocs]

Marked version:0.6.2

Markdown flavor: CommonMark

Description

Fixed commonmark example 40 and example 57, and related issue #1474

Example40

Markdown content
foo
    # bar

Expected Html
<p>foo
# bar</p>

Acutral html
<p>foo</p>
<pre><code># bar</code></pre>

Example57

Markdown content
Foo
    ---

Expected Html
<p>Foo
---</p>

Actural Html
<h2>Foo</h2>

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