feat: upgrade marked

[541xxx]

Summary
Upgrade marked
Resolved #722
Related Marked #1466

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:

1. Drop support for Node v0.10 and old browsers such as Internet Explorer
2. You should not have any problems if using Node 4+ or a modern browser
   Add parameter slugger to Renderer.prototype.heading method #1401
   You should not have any problems if you do not override this method

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)

[andywhite37]

Bumping this PR, as it also fixes a security alert that we just started getting for marked (which comes in as a dependency of docsify).

WS-2019-0024
More information
moderate severity
Vulnerable versions: >= 0.5.0, < 0.6.1
Patched version: 0.6.1

A flaw was found in nodejs-marked versions from 0.5.0 to before 0.6.1. Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS). Input to the host variable is vulnerable when input contains parenthesis in link URIs, coupled with a high number of link tokens in a single line.

[awm086]

might make more sense to go to 0.7.0 because I am seeing this:

───────────────┬──────────────────────────────────────────────────────────────┐
│ Low           │ Regular Expression Denial of Service                         │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Package       │ marked                                                       │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Patched in    │ >=0.7.0                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Dependency of │ docsify-cli [dev]                                            │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Path          │ docsify-cli > docsify > marked                               │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ More info     │ https://npmjs.com/advisories/1076  

[anikethsaha]

Thanks for the PR. But this has been fixed already.
🙏