PVME syntax highlighting

[Towsti]

Highlight markdown, json (embed), and PVME commands in the editor

[rsnx222]

not sure what this means, can we close it? @Towsti

[Towsti]

Idea is to colour pvme syntax/keywords in the text input to more easily distinguish between text and commands.

Eg colour bot commands blue:

• \n.
• \n.tag:headings
• $linkmsg_tagword$

Addition could be to include json + markdown highlighting

Feel free to close if not required