Support html subset from Matrix

[binarious]

Is your feature request related to a problem? Please describe.
Using Markdown (like **bold** text or [My Link](https://myurl.com)) results in plain text instead of a Markdown interpreted message.

Describe the solution you'd like
It would be great to have the message Markdown interpreted.

[oelison]

In the matrix protocol only html is defined. And also only a subset.
So what I could assume is to open an interface for html messages. The results will be very different on each client. So it is on the users side to try out what is working.
Element for example is converting the markdown input into html. You could see the result when you look at the code of a send message. But it looks very complex. Please give a comment on the approach.

[oelison]

See:
matrix-org/matrix-spec-proposals#1225
matrix-org/matrix-spec-proposals#1562

[oelison]

{
  "type": "m.room.message",
  "sender": "@abcde:abcde.de",
  "content": {
    "body": "test **with mark down**",
    "msgtype": "m.text",
    "format": "org.matrix.custom.html",
    "formatted_body": "test <strong>with mark down</strong>"
  },
  "origin_server_ts": 13242342316,
  "unsigned": {
    "age": 1
  },
  "event_id": "$AAAAAAAAAAAAAAA_A_AAAAA-AAAAAAAAAAAAAAA",
  "room_id": "!AAAAAAAAAAAAA:abcde.de"
}

[binarious]

I see. Didn't know that. HTML support would be nice then, if that's feasable. Shall I rename the issue?

[oelison]

I have renamed it.

[oelison]

Looks fine. See one result copied into #test-ioBroker-adapter:matrix.org

[binarious]

I just see 12ab as an unformatted message in Element on Android.

Edit: Just read the updated Readme which clearly states that as the expected result.
Edit 2: Looks good on Element Web. 🎉