Add support for Wiki links

[Nebucatnetzer]

There a currently a lot of note taking applications getting made which are inspired by the Zettelkasten method.
A lot of those apps started adopting the wiki link format to link notes together. [[Note Name]]
I'm currently using Obsidian.md on the desktop to work with my notes but on the go I'm using Nextcloud Notes.
Therefore I have a lot of notes with links to each other but the links aren't working in the Android application or the web application.

Describe the solution you'd like
Add support for the Wiki link, link format. So that one can use:
[[Note Name]] to link to a file
and
[[Note Name#Heading]] to link to a heading.

[stefan-niedermann]

Since we plan to migrate to Nextcloud Text as markdown renderer in the future, i vote against adding new syntax support which is not supported by Nextcloud Text at this time.

[Nebucatnetzer]

I don't have problem with opening an issue about this on the Nextcloud Text project. Sep 26, 2020 17:47:38 Niedermann IT-Dienstleistungen <notifications@github.com>:

…

Since we plan to migrate to Nextcloud Text[#331] as markdown renderer in the future, i vote against adding new syntax support which is not supported by Nextcloud Text at this time. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub[#616 (comment)], or unsubscribe[https://github.com/notifications/unsubscribe-auth/AAROM5OJ7NPK67DMMQG2SJLSHYEJBANCNFSM4R26QUHQ]. [https://github.com/notifications/beacon/AAROM5PCAY5CDLGHRAMW63LSHYEJBA5CNFSM4R26QUH2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOFGY3MZA.gif]

[stefan-niedermann]

@Nebucatnetzer if @korelstar (maintainer of this repo) agrees, i think this would make more sense for a consistent feature set across all Nextcloud apps which use markdown.

[Nebucatnetzer]

I created the issue at Nextcloud Text but will keep this issue here open as well at least until we have a response from upstream.

[korelstar]

I agree with @stefan-niedermann, but we can leave this open until we finished switching to Text

[newhinton]

So, is switching to nextcloud text even an option? The current issues with their implementation would be a dealbreaker for me.

Also it seems this wouldn't be too hard to implement, so i'd give it a try

[korelstar]

You're right, switching to Nextcloud Text is currently not an option due to the critical issues (see #652).

However, I'm still against introducing a new non-Markdown syntax.