feat: Mobile text copying

[Scyye]

Please describe the feature you'd like
A button on messages modmail sends, that when clicking them, it replies (ephemerally, which is part of the motivation for buttons) with a plain message with the message content.

Describe the motivation for the feature
Suggestion #203
Suggestion #232
Suggestion #351
Discord on ios doesnt play nicely with embeds and copying content from them, but it works fine on actual messages, using the "Copy Text" button
This would also be useful when copying content such as on snippets, where on desktop, you cant easily copy markdown inside embeds.

Describe alternatives you've considered
Dont use embeds, which is just stupid. (ex. Suggestion #222, or almost any occurrence of "Compact mode")

Additional context
Buttons will most likely be standard for most things once #162 is resolved, so this obviously isnt viable until after then.