adding a character count

### Problem I have

in the context of:
the exponential user growth of a new instance with an hard limit at 300 chars, rendering all bigger post as external links.

### Solution I'd like

i'd like to have a char count that give an alert when you pass a certain value like 300, but keep allowing you to type.
Something like all characters after 300 are rendered in red while typing.

That way i can decide, if my answer is relatively on their limit, to short it
Or if it's a long form, to send it anyway

### Alternatives considered

_No response_

### Other

_No response_