Feature Request: Support local wikilink namespace and external namespace like MediaWiki does.

Proposal is WIP

I am personally interested in working on this feature

Is your feature request related to a problem? Please describe.
I want the WikiLink to be expandable. Currently wikilink in vscode-markdown-notes organize all wikilink in a plain directory. It's a bit hard to organize as the number of markdown files scale up. Inspired by Wikipedia I like to propose a format of wikilink that's forward expandable, and backward compatible.

Describe the solution you'd like

Support local wikilink namespace and external namespace like MediaWiki does.

[[namespace:anther-topic| Another Topic]]: renders as Another Topic
[[:external-namespace:external-sub-namespace:anther-topic| Third Topic]]: renders as Third Topic where as the external URI can be configured, and has a default, such as supporting Wikipedia sites just like you can write [[en:Earth]] to point to Earth topic on English Wikipedia from any given Wikipedia language site or other Wikimedia sites.

So, in Wikipedia, name space works like this:

[[Earth]] is the default namespace of article "Earth"
[[Talk:Earth]] is the "Talk" namespace of Earth, which represents a discussion for page Earth.

Locally, it can be used to point to multiple directories. For example

[note:my-project-meeting]]: point to file:///<dir root>/note/my-project-meeting.md
[people:join-smith]]: point to file:///<dir root>/people/john-smith.md

Or configuration can point to a different directory

{
  namespaces: [{
     name: "note", relativePath: 'note/'
  }, {
     name: "people", relativePath: 'people/'
  }, {
     name: "log", relativePath: '../data/log/'
  }]
}

We can also create cross-domain or cross-protocol external namespace
such as [[:wikidata:Q123456]]
With external namespace

{
  external_namespaces: [{
   name: 'wikidata', reference:'https://www.wikidata.org/wiki/%s'
  }] 
}

TODO(xinbenlv): 2020-12-01 complete this proposal.

Describe alternatives you've considered
I have considered using [link name](href).

Additional context
See https://www.mediawiki.org/wiki/Help:Links#Internal_links

This is possible with allowPipedWikiLinks:

vscode-markdown-notes/package.json

Line 136 in 311dda9

"vscodeMarkdownNotes.allowPipedWikiLinks": {

@kortina great to know piped links are supported. Are namespaces supported?

Oh, hmm, no, those are not supported - so is the idea disambiguation when there are multiple meanings for the same word?

Would the file name on disk be namespace:anther-topic.md for [[namespace:anther-topic| Another Topic]] ?

So, in Wikipedia, name space works like this:

[[Earth]] is the default namespace of article "Earth"
[[Talk:Earth]] is the "Talk" namespace of Earth, which represents a discussion for page Earth.

Locally, it can be used to point to multiple directories. For example

[note:my-project-meeting]]: point to file:///<dir root>/note/my-project-meeting.md
[people:join-smith]]: point to file:///<dir root>/people/john-smith.md

Or configuration can point to a different directory

{
  namespaces: [{
     name: "note", relativePath: 'note/'
  }, {
     name: "people", relativePath: 'people/'
  }, {
     name: "log", relativePath: '../data/log/'
  }]
}

We can also create cross-domain or cross-protocol external namespace
such as [[:wikidata:Q123456]]
With external namespace

{
  external_namespaces: [{
   name: 'wikidata', reference:'https://www.wikidata.org/wiki/%s'
  }] 
}

Remove old proposal portion

The existing format looks like this

[[default-topic.md]]: already supported

[[default-topic]]: already supported

I like to propose it to support Topic alias

[[default-topic.md | Default Topic]], renders as Default Topic

[[default-topic | Default Topic]], renders as Default Topic