Update Leafdoc

[johnd0e]

Latest Leafdoc is still unpublished on npm, so Leaflet documentation is building with outdated Leafdoc.

The issue is already reported a year ago.

Besides of functionality, outdated Leafdoc currently is the source of critical vulnerabilities reported by npm during install (see #7133 (comment)).

[mondeja]

I think that this pull can be merged to remove a security vulnerability during install.

Related to, this Leaflet issue has been closed but the error persists with current Leaflet master because Leafdoc has not been released after removing sander dependency, that was the source of the error.

So yes, we need a new Leafdoc version published in NPM:

• Bump Leafdoc version to 1.6.0.
• Publish it on NPM.
• Bump Leafdoc version dependency in Leaflet package.json.

[IvanSanchez]

I've been working on some (IMO much-needed) cleanup of the leafdoc regexes. Before publishing a new Leafdoc version, I'd appreciate any review of Leaflet/Leafdoc#52

[Falke-Design]

Version 2.3.0 of Leafdoc released on npm: https://www.npmjs.com/package/leafdoc