Add writer(s) characters

[silopolis]

It would be nice to have some writer(s) character(s) in the list and/or allow defining custom ones like for prompts.

I believe generating textual content (creative/non-creative, fiction or not) is one of the most important usages of chat AIs, so having corresponding characters seems too.

Of course, being able to create custom characters may widely open the feature to any use cases.