text: Title: Email column type
  Body: We don't have an email column type at the moment. It's because Postgres doesn't have an email column type.
  
  However, I think it would be useful to designate a column as containing an email.
  
  ## Option 1
  
  We can define a new column type, which basically just inherits from `Varchar`:
  
  ```python
  class Email(Varchar):
      pass
  ```
  
  ## Option 2
  
  Or, let the user annotate a column as containing an email.
  
  One option is using [Annotated](https://docs.python.org/3/library/typing.html#typing.Annotated), but the downside is it was only added in Python 3.9:
  
  ```python
  from typing import Annotated
  
  class MyTable(Table):
      email: Annotated[Varchar, 'email'] = Varchar()
  ```
  
  Or something like this instead:
  
  ```python
  class MyTable(Table):
      email = Varchar(validators=['email'])
  ```
  
  ## Benefits
  
  The main reason it would be useful to have an email column is when using [create_pydantic_model](https://piccolo-orm.readthedocs.io/en/latest/piccolo/serialization/index.html#create-pydantic-model) to auto generate a Pydantic model, we can set the type to `EmailStr` (see [docs](https://pydantic-docs.helpmanual.io/usage/types/)).
  
  ## Input
  
  Any input is welcome - once we decide on an approach, adding it will be pretty easy.