Autolink edge case: underscores in url

[digitalmoksha]

Ran across this,

Given http://example.com/src/_mocks_/vscode.js

• comrak: <p><a href="http://example.com/src/">http://example.com/src/</a><em>mocks</em>/vscode.js</p>
• cmark-gfm: <p><a href="http://example.com/src/_mocks_/vscode.js">http://example.com/src/_mocks_/vscode.js</a></p>

Looks like the underscores are getting recognized as markdown

Related to #382