Support ftp scheme for markdown URLs

[Arnavion]

Currently it's not output as an anchor.

Source: Get foo.txt from [here.](ftp://example.com/foo.txt)

Live: Get foo.txt from here.

[JuanitoFatas]

Hello @Arnavion,

You could add another pipeline to allow more schemes in your application. Please see the rationale behind this in #104 and #39.

Thanks for checking in! 😊

[Arnavion]

My intention was to have this for github.com

Regarding the security concern:

1. Major browsers support FTP themselves instead of requiring a separate client.
2. You support mailto, which does require a separate client, and has a much wider history of causing ACE via buffer overflows (eg: ridiculously long subject lines) in said clients.

[JuanitoFatas]

/cc @jch

[simeonwillbanks]

@Arnavion We're closing this issue:

If anyone ... has a markup related feature request, please write in to [email protected]. It'll be easier for us to track from there. Thanks!

— @jch

Thanks for understanding!

[mojavelinux]

Interesting to note that this seems to work fine for AsciiDoc files.

[kerner1000]

Hey,
this does not work if you include username and password in the link.
E.g.
ftp
(ftp://user:[email protected]/mydata)