Editor assumes .txt are markdown syntax

[provokateurin]

Steps to reproduce

1. Go to settings and change file extension to .txt
2. Create a new note
3. Edit it and enter markdown syntax like #

Expected behaviour

The editor should not react to/interpret the input and file content as markdown syntax.

Actual behaviour

The editor just assumes the content and input is markdown and thus renders it that way.

Server

Please complete the following information.

• Notes app version: 4.9.0-beta.2
• Nextcloud version: 28.0.0 beta 2
• OS: Linux
• Web server: PHP standalone
• PHP version: 8.2
• Database: sqlite

[provokateurin]

This happens with both the rich text mode and the edit mode (although it is worse with the rich text mode imo)

[joshtrichards]

Related: #1010