How to set comments for columns
Peewee does not add comments to the schema. Is this functionality you would be interested in having as part of peewee? 

I already have code I could easily adapt to a PR.

@pch18 A solution for you could look something like this:
``` python
import peewee as pw


class DatabaseComment(pw.Node):
    def __init__(self, obj, comment, obj_type):
        self.obj = obj
        self.comment = comment
        self.obj_type = obj_type

    def __sql__(self, ctx):
        ctx.literal('COMMENT ON ')
        ctx.literal(self.obj_type)
        ctx.literal(' ')
        with ctx.scope_values():
            if isinstance(self.obj, pw.Field):
                ctx.sql(self.obj.model).literal('.')
            ctx.sql(self.obj)

        ctx.literal(' IS ')
        ctx.sql(self.comment)
        return ctx

        
# >>> datababase.execute(DatabaseComment(SomeTable, 'Hello world', 'TABLE'))
```
I tried to set the help_text field, it didn't seem to work